Plating apparatus and plating method

ABSTRACT

A substrate treating apparatus provided with a plating unit, a bevel etching unit, a cassette stage on which a cassette for accommodating a wafer and a cassette for accommodating a dummy wafer are placed, and a transport robot for transporting the wafer or the dummy wafer among the cassettes, the plating unit and the bevel etching unit. The plating unit is capable of performing a copper plating process on the wafer and the dummy wafer, and the bevel etching unit is capable of etching a peripheral edge of the wafer and etching away a copper film formed on the dummy wafer.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a plating apparatus and a plating method for plating a substrate such as a semiconductor wafer with copper.

[0003] 2. Description of Related Art

[0004] In the production of a semiconductor device, a plating process is often performed for plating one surface of a semiconductor wafer (hereinafter referred to simply as “wafer”). A typical plating apparatus for plating a wafer with copper includes a plating vessel which contains a copper-ion-containing plating liquid to be brought into contact with one surface of the wafer, an anode disposed in the plating vessel, and a cathode to be brought into contact with the wafer.

[0005] For the plating, the cathode is kept in contact with the wafer, and one surface (lower surface) of the wafer is kept in contact with the plating liquid filled in the plating vessel. In this state, the anode and the cathode are electrically energized. Thus, electrons are donated to copper ions in the plating liquid in the interface between the surface of the wafer and the plating liquid, so that copper atoms are deposited on the surface of the wafer.

[0006] Exemplary methods for replenishment of copper ions consumed by the plating in the plating liquid are to employ a dissolvable copper anode which is per se dissolvable in the plating liquid, and to employ an anode non-dissolvable in the plating liquid and a copper supply source provided separately from the anode.

[0007] Where the dissolvable anode is employed, the plating process can stably be performed with the surface of the anode being covered with a so-called black film. The black film can be kept stable only when the anode is electrically energized in the same cycle. When the plating apparatus is not in use for a long period, the anode is liable to deteriorate. Therefore, the plating process cannot properly be performed when resumed.

[0008] To overcome this drawback, Japanese Unexamined Patent Publication No. 2000-119900 proposes that the anode is continuously electrically energized with a dummy cathode disposed in the plating vessel even when a plating apparatus is not in use. In the prior-art plating apparatus and plating method, copper is deposited on the dummy cathode when the anode and the dummy cathode are electrically energized. The literature states that copper deposited on the dummy cathode is etched by the plating liquid when the dummy cathode is not electrically energized and, therefore, no maintenance is required without accumulation of copper on the dummy cathode.

[0009] However, the operation (burn-in) intervals of the plating apparatus and the amperage applied during the operation of the plating apparatus may vary, and the etching rate at which copper deposited on the dummy cathode is etched by the plating liquid may vary depending on the type of the plating liquid. Therefore, it is not always guaranteed that the dummy cathode is free from accumulation of copper.

[0010] Further, the presence of the dummy cathode in the plating vessel may adversely affect the uniformity of the thickness of a plated film in the ordinary plating process. Therefore, conditions such as the size of the dummy cathode and the position of the dummy cathode in the plating vessel should be optimized to ensure the uniformity of the plated film thickness. However, it is difficult to find the optimized conditions.

[0011] When the plating apparatus is not in use for a long period, parts of the plating apparatus supplied with the plating liquid during the plating process are liable to dry, so that constituents of the plating liquid may be crystallized. In a small-size droplet of the plating liquid, the crystallization occurs in about one to two hours. Where the plating apparatus is adapted to perform the plating process with a peripheral edge portion of the wafer being sealed by a cathode ring, crystals attributable to the plating liquid are liable to grow on a sealing surface of the cathode ring, resulting in a temporary sealing failure. In addition, the crystals may damage the sealing surface to cause a permanent sealing failure.

[0012] While problems associated with the use of the dissolvable anode have been described, the use of the non-dissolvable anode also has drawbacks. That is, when the plating apparatus is not in use for a long period, the surface of the copper supply source is irreversibly deteriorated. Therefore, the plating process cannot properly be performed when resumed. If the prior-art construction and method described in the aforesaid literature are employed, it is expected that similar problems occur when the plating liquid is electrically energized during the halt of the plating apparatus.

SUMMARY OF THE INVENTION

[0013] It is an object of the present invention to provide a plating apparatus which is capable of properly performing a plating process.

[0014] It is another object of the present invention to provide a plating apparatus which comprises a sealing member for sealing a peripheral edge portion of the wafer and is generally free from a sealing failure of the sealing member.

[0015] It is further another object of the present invention to provide a plating method which is capable of properly performing a plating process.

[0016] It is still another object of the present invention to provide a plating method which is employed in a plating apparatus comprising a sealing member for sealing a peripheral edge portion of the wafer and is generally free from a sealing failure of the sealing member.

[0017] A plating apparatus (10) according to a first aspect of the present invention comprises: a plating unit (20 a to 20 d) for performing a plating process with the use of a plating liquid for plating a to-be-treated substrate (W) with copper; a dummy substrate container (Cd) for accommodating a dummy substrate (D) having a surface formed with an electrically conductive film; a dummy substrate transport mechanism (TR, 18) for transporting the dummy substrate between the plating unit and the dummy substrate container; a substrate loading discontinuation detecting mechanism (155) for detecting discontinuation of loading of the to-be-treated substrate in the plating unit; and a control section (155) which performs a control operation so as to transport the dummy substrate from the dummy substrate container into the plating unit by means of the dummy substrate transport mechanism and perform the plating process on the surface of the dummy substrate formed with the electrically conductive film in the plating unit in response to the detection of the discontinuation of the loading of the to-be-treated substrate in the plating unit by the substrate loading discontinuation detecting mechanism. The components represented by the parenthesized alphanumeric characters are equivalent to those to be described in the following embodiment. However, it should be understood that the present invention be not limited to the embodiment. This definition is also applied to the following description.

[0018] According to this inventive aspect, the plating process can be performed on the dummy substrate in the plating unit (this process will be hereinafter referred to as “dummy plating process”) after the discontinuation of the loading of the to-be-treated substrate in the plating unit. At this time, a cathode is brought into contact with the electrically conductive film of the dummy substrate, and an anode is provided in the plating liquid for electrolytic plating. Therefore, copper ions are continuously leached out of a copper supply source into the plating liquid even when the plating process is not performed on the to-be-treated substrate. Thus, the copper supply source can be kept in a proper surface state.

[0019] The copper supply source may be the anode per se where a dissolvable anode is employed as the anode, or may be provided separately from the anode where a non-dissolvable anode is employed as the anode. Where the copper supply source is the dissolvable anode, a black film formed on the surface of the dissolvable anode can be stabilized by the dummy plating process. Where the non-dissolvable anode is employed, the dummy plating process makes it possible to prevent irreversible deterioration of the surface of the copper supply source provided separately from the anode. Therefore, the to-be-treated substrate can properly be plated with copper, when the plating process on the to-be-treated substrate is resumed.

[0020] The discontinuation of the loading of the to-be-treated substrate in the plating unit herein means, for example, that the plating process on wafers in one production lot is completed. The to-be-treated substrate may be, for example, a semiconductor wafer (hereinafter referred to simply as “wafer”).

[0021] Some plating apparatuses for the plating of the wafer include a sealing member for sealing a peripheral edge portion of the wafer to keep the plating liquid away from the cathode and a portion of the wafer not to be plated. The sealing member is kept wetted with the plating liquid during the plating process.

[0022] In this case, the sealing member is kept wetted with the plating liquid by performing the dummy plating process when the plating process is not performed on the to-be-treated substrate. That is, the crystallization of constituents of the plating liquid can be prevented, which may otherwise occur when the sealing member wetted with the plating liquid is dried. Therefore, a sealing failure due to the presence of crystals on the sealing member and a sealing failure due to a damage to the sealing member by the crystals can be suppressed. The sealing member may be provided, for example, on a cathode ring having a cathode.

[0023] In the inventive plating apparatus, the dummy substrate is automatically transported from the dummy substrate container to the plating unit for the dummy plating process under the control of the control section in response to the detection of the discontinuation of the loading of the to-be-treated substrate in the plating unit by the substrate loading discontinuation detecting mechanism. Since the dummy substrate is accommodated in the dummy substrate container in the plating apparatus, there is no need for an operator to load the dummy substrate into the plating apparatus. Therefore, the dummy plating process is automatically started without the intervention of the operator, when the loading of the to-be-treated substrate in the plating unit is discontinued.

[0024] The inventive plating apparatus may further comprise a film removing unit (21 a, 21 b) for performing a copper film removing process for removing a copper film formed on the dummy substrate subjected to the plating process in the plating unit. In this case, the electrically conductive film maybe resistant to the copper film removing process performed in the film removing unit.

[0025] With this arrangement, the copper film formed on the dummy substrate can be removed in the film removing unit. At this time, the electrically conductive film of the dummy substrate is not removed, because the electrically conductive film is resistant to the copper film removing process. Since the electrolytic plating process can be performed again via the electrically conductive film, the dummy substrate from which the copper film has been removed can be reused for the dummy plating process. That is, the dummy substrate can repeatedly be used, so that the plating apparatus obviates the need for the operator to frequently perform a maintenance operation.

[0026] The copper film removing process, which is performed in the film removing unit provided separately from the plating unit, does not influence the plating process performed in the plating unit. Therefore, the plating apparatus can properly perform the plating process on the to-be-treated substrate. Further, the plating unit does not influence the copper film removing process performed in the film removing unit. Therefore, optimum conditions for complete removal of the copper film can be employed in the copper removing unit, so that the dummy plating process can properly be performed with the use of the dummy substrate from which the copper film has been completely removed.

[0027] The plating apparatus may further comprise an additional unit for performing a process other than the plating process (e.g., a bevel etching unit for etching a peripheral edge of the to-be-treated substrate subjected to the plating process). The additional unit may function as the film removing unit. Alternatively, the film removing unit may be a unit dedicated to the film removing process.

[0028] The removal of the copper film may be achieved by electrolytic etching or with the use of an etching liquid.

[0029] Exemplary materials for the dummy substrate include semiconductors (e.g., silicon) , glass materials, ceramic materials, resins and metals. Exemplary materials for the electrically conductive film include gold (Au) and platinum (Pt). Where the film removing unit performs the copper film removing process by etching away the copper film with the use of a mixture of sulfuric acid, a hydrogen peroxide and water (an etching liquid), for example, the electrically conductive film of gold or platinum has an etching resistance, i.e., a resistance to the etching liquid.

[0030] The inventive plating apparatus may further comprise a cassette stage (16) for receiving thereon a cassette (Cw) capable of accommodating the to-be-treated substrate to be subjected to the plating process in the plating unit. In this case, the dummy substrate container may be a cassette (Cd) disposed on the cassette stage.

[0031] With this arrangement, where the plating apparatus includes the cassette stage, the cassette placed on the existing cassette stage can be used as the dummy substrate container without the need for separately providing a dedicated dummy substrate container. The to-be-treated substrate and the dummy substrate may have the same shape and size. In this case, the cassette for accommodating the to-be-treated substrate can be employed as the cassette for accommodating the dummy substrate.

[0032] The dummy substrate transport mechanism may double as a transport mechanism for transporting the to-be-treated substrate between the cassette placed on the cassette stage and the plating unit.

[0033] The dummy substrate container may be a container other than the cassette placed on the cassette stage, or a dedicated container disposed in any other position in the plating apparatus.

[0034] In the plating apparatus having the aforesaid construction, the plating unit may include a plurality of plating units, and the dummy substrate may include a plurality of dummy substrates whose number is greater than the number of the plating units. In this case, the dummy substrate container may be capable of accommodating all the dummy substrates.

[0035] The drying of the sealing member wetted with the plating liquid occurs in each of the plating units. With the aforesaid arrangement, the dummy plating process can be performed simultaneously in the respective plating units. Therefore, the crystallization attributable to the drying of the sealing member can be prevented in each of the plating units. Thus, a sealing failure of the sealing member can be suppressed in each of the plating units.

[0036] When the plating process is performed on to-be-treated substrates in some of the plural plating units, the dummy plating process may be performed in the other plating units. Therefore, the sealing failure of the sealing member can be suppressed in each of the plating units.

[0037] A plating apparatus (10) according to a second aspect of the present invention comprises: a plating unit (20 a to 20 d) for performing a plating process with the use of a plating liquid for plating a to-be-treated substrate (W) with copper; and a film removing unit (21 a, 21 b) for performing a copper film removing process for removing a copper film formed on a dummy substrate (D) subjected to the plating process in the plating unit.

[0038] According to this inventive aspect, copper ions are supplied to the plating liquid from a copper supply source to keep the copper supply source in a proper surface state by a dummy plating process, even when the plating process is not performed on the to-be-treated substrate.

[0039] Therefore, the to-be-treated substrate can properly be plated with copper, when the plating process on the to-be-treated substrate is resumed.

[0040] Where the plating apparatus includes a sealing member, the sealing member is kept wetted with the plating liquid by performing the dummy plating process even when the plating process is not performed on the to-be-treated substrate. That is, crystallization of constituents of the plating liquid is prevented, which may otherwise occur when a sealing member wetted with the plating liquid is dried. Therefore, a sealing failure due to the presence of crystals on the sealing member and a sealing failure due to a damage to the sealing member by the crystals can be suppressed.

[0041] Further, the copper film formed on the dummy substrate by the plating can be removed in the film removing unit. Where the dummy substrate has an electrically conductive film formed on one surface thereof and having a resistance to the copper film removing process performed in the film removing unit and the plating process is to be performed on the surface of the dummy substrate formed with the electrically conductive film in the plating unit, the dummy substrate can be reused for the dummy plating process after the removal of the copper film.

[0042] A plating method according to the present invention comprises the steps of: detecting discontinuation of loading of a to-be-treated substrate (W) in a plating unit (20 a to 20 d) which is adapted to perform a plating process for plating the to-be-treated substrate (W) with copper; and transporting a dummy substrate (D) having a surface formed with an electrically conductive film from a dummy substrate container (Cd) into the plating unit, and performing a dummy plating process in the plating unit for plating the surface of the dummy substrate formed with the electrically conductive film after the detecting step.

[0043] The inventive plating method may further comprise the step of transporting the dummy substrate into a film removing unit (21 a, 21 b) which is adapted to perform a copper film removing process, and removing a copper film formed on the dummy substrate by the dummy plating process in the film removing unit after the dummy plating step. In this case, the electrically conductive film may be resistant to the copper film removing process performed in the film removing unit.

[0044] Where a plurality of plating units are provided, the dummy plating step may comprise the step of performing the dummy plating process simultaneously in the respective plating units.

[0045] Another plating method according to the present invention comprises the steps of: transporting a dummy substrate (D) into a plating unit (20 a to 20 d) which is adapted to perform a plating process for plating a to-be-treated substrate (W) with copper, and performing a dummy plating process in the plating unit for plating the dummy substrate with copper, when the plating process is not performed on the to-be-treated substrate in the plating unit; and transporting the dummy substrate having a copper film formed by the dummy plating process into a film removing unit (21 a, 21 b) which is adapted to perform a copper film removing process, and removing the copper film formed on the dummy substrate in the film removing unit after the dummy plating step.

[0046] The foregoing and other objects, features and effects of the present invention will become more apparent from the following description of the preferred embodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0047]FIG. 1 is a block diagram illustrating the construction of a substrate treating apparatus according to one embodiment of the present invention;

[0048]FIG. 2 is a schematic plan view of a wafer treating section;

[0049]FIG. 3(a) is a schematic plan view for explaining the construction of a robot body provided in the wafer treating section;

[0050]FIG. 3(b) is a schematic side view for explaining the construction of the robot body provided in the wafer treating section;

[0051]FIG. 3(c) is a schematic front view for explaining the construction of the robot body provided in the wafer treating section;

[0052]FIG. 4(a) is a schematic plan view of a cassette stage on which a cassette is placed;

[0053]FIG. 4(b) is a schematic side view of the cassette stage on which the cassette is placed;

[0054]FIG. 5 is a schematic front view illustrating the construction of a plating section;

[0055]FIG. 6 is a diagram illustrating a relationship between the concentrations of copper in plating liquid samples and measured absorbances;

[0056]FIG. 7 is a schematic sectional view illustrating the construction of a plating unit;

[0057]FIG. 8 is a schematic sectional view illustrating a portion around a wafer as observed in a plating process;

[0058]FIG. 9 is a schematic sectional view illustrating the plating unit with a spin base facing upward;

[0059]FIG. 10 is a schematic sectional view illustrating the construction of a bevel etching unit;

[0060]FIG. 11 is a schematic sectional view illustrating the construction of a cleaning unit;

[0061]FIG. 12 is a block diagram illustrating the construction of a control system for the wafer treating section;

[0062]FIG. 13 is a schematic diagram illustrating the construction of a major constituent managing section; and

[0063]FIG. 14 is a block diagram illustrating the construction of control systems for the major constituent managing section, a minor constituent managing section and a post-treatment agent supplying section.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0064]FIG. 1 is a block diagram illustrating the construction of a substrate treating apparatus 10 according to one embodiment of the present invention.

[0065] The substrate treating apparatus 10 includes a wafer treating section 1 for plating a surface of a semiconductor wafer (hereinafter referred to simply as “wafer”) with the use of a plating liquid and etching (bevel-etching) a peripheral edge of the wafer after the plating, a major constituent managing section 2 having a copper supply source for supplying copper ions to the plating liquid for management of the concentrations of major constituents of the plating liquid, a minor constituent managing section 3 for managing minor constituents of the plating liquid, and a post-treatment agent supplying section 4 for supplying a post-treatment agent to the wafer treating section 1 for post-treatment of the wafer after the plating. The substrate treating apparatus 10 is disposed in a clean room.

[0066] The plating liquid for use in the wafer treating section 1 contains sulfuric acid (supporting electrolyte) copper ions (target metal), iron (oxidizing/reducing agent) and water as major constituents thereof. The plating liquid further contains chlorine, a plating retarding additive and a plating accelerating additive as minor constituents thereof.

[0067] Two plating liquid transport pipes P12 a, P12 b extend between the wafer treating section 1 and the major constituent managing section 2 for transporting the plating liquid between these sections in opposite directions. Similarly, two plating liquid transport pipes P13 a, P13 b extend between the wafer treating section 1 and the minor constituent managing section 3 for transporting the plating liquid between these sections in opposite directions. Further, a post-treatment agent pipe P14 extends between the wafer treating section 1 and the post-treatment agent supplying section 4 for supplying the post-treatment agent from the post-treatment agent supplying section 4 to the wafer treating section 1.

[0068] The wafer treating section 1 includes a system controller for controlling the entire substrate treating apparatus 10. The wafer treating section 1 is connected to the major constituent managing section 2, the minor constituent managing section 3 and the post-treatment agent supplying section 4 via signal lines L12, L13 and L14, respectively. The operations of the major constituent managing section 2, the minor constituent managing section 3 and the post-treatment agent supplying section 4 are controlled by the system controller provided in the wafer treating section 1.

[0069] The plating liquid being used in the wafer treating section 1 is transported (sampled) into the minor constituent managing section 3 through the plating liquid transport pipe P13 a. The minor constituent managing section 3 is capable of analyzing at least one of the minor constituents through a CVS (cyclic voltammetric stripping) analysis. The minor constituent managing section 3 includes a minor constituent management controller, which is capable of calculating the amounts of the minor constituents to be added to the plating liquid in the wafer treating section 1 based on the result of the CVS analysis so as to adjust the concentrations of the minor constituents of the plating liquid within predetermined concentration ranges. Under the control of the minor constituent management controller, the minor constituents are supplied in the amounts thus calculated to the plating liquid in the wafer treating section 1 through the plating liquid transport pipe P13 b.

[0070] The post-treatment agent supplying section 4 includes an agent tank containing the post-treatment agent, and an agent supply mechanism for supplying the post-treatment agent from the agent tank to the wafer treating section 1. Examples of the post-treatment agent include an etching liquid to be used for the bevel etching and a cleaning liquid.

[0071]FIG. 2 is a schematic plan view of the wafer treating section 1.

[0072] The wafer treating section 1 is adapted to perform a plating process for forming a thin copper film on the surface of the wafer W, then perform an etching process for etching the peripheral edge of the wafer W, and perform a cleaning process for cleaning the entire surfaces of the wafer W.

[0073] A wafer loading/unloading section 19 is disposed along a first transport path 14 extending linearly horizontally. In the wafer loading/unloading section 19, a plurality of cassette stages 16 (four cassette stages in this embodiment) which are each adapted to receive thereon one cassette C capable of accommodating a wafer W are arranged along the first transport path 14.

[0074] A cassette Cd disposed at one end of the wafer loading/unloading section 19 accommodates a dummy wafer D instead of the wafer W, and the other three cassettes Cw each accommodate a to-be-treated wafer W. Four or more dummy wafers D are provided in the wafer treating section 1, and the cassette Cd is capable of accommodating all the dummy wafers D.

[0075] The wafer W has a generally round shape and, for example, is a silicon substrate having a multiplicity of fine holes or grooves formed in a to-be-treated surface thereof and a barrier layer and a seed layer formed on the surface thereof. The dummy wafers D each have the same shape and size as the wafer W and, for example, are composed of silicon. The dummy wafers D each have an electrically conductive film formed on one surface thereof by plating. The dummy wafers D may be composed of a semiconductor other than silicon, a glass material, a ceramic material, a metal or a resin

[0076] The electrically conductive film has an electrical conductivity, and functions as a seed layer during the plating. Further, the electrically conductive film has an etching resistance, and is resistant to an etching liquid (e.g., a mixture of sulfuric acid, a hydrogen peroxide aqueous solution and water) for use in the etching of copper. The electrically conductive film is composed of gold (Au) or platinum (Pt), for example.

[0077] A second linear transport path 15 is provided horizontally and perpendicularly to the first transport path 14. In this embodiment, the second transport path 15 extends from a middle portion of the first transport path 14. A plating section 12 including four plating units 20 a to 20 d arranged along the second transport path 15 is provided on one side of the second transport path 15. Therefore, the number of the dummy wafers D provided in the wafer treating section 1 is equal to or greater than the number of the plating units 20 a to 20 d.

[0078] The plating units 20 a to 20 d are each adapted to plate the surface of the wafer W or the dummy wafer D with copper. The dummy wafers D are subjected to the plating process in the plating units 20 a to 20 d, when the plating process is not performed on the wafer W.

[0079] A post-treatment section 13 including two bevel etching units 21 a, 21 b and two cleaning units 22 a, 22 b arranged along the second transport path 15 is provided on the other side of the second transport path 15. The bevel etching units 21 a, 21 b are each adapted to etch the peripheral edge of the wafer W and to etch away a copper film formed on one entire surface of the dummy wafer D by the plating. The cleaning units 22 a, 22 b are each adapted to clean opposite surfaces of the wafer W.

[0080] The first transport path 14 and the second transport path 15 constitute a T-shaped transport path, and a single transport robot TR is provided on the T-shaped transport path. The transport robot TR includes transport guide rails 17 disposed along the second transport path 15, and a robot body 18 movable along the transport guide rails 17. The operation of the transport robot TR is controlled by a transport controller 29.

[0081] The robot body 18 is capable of transporting the wafer W along the first transport path 14 and along the second transport path 15. Therefore, the robot body 18 can access any of the cassettes C placed on the cassette stages 16 to load and unload a wafer W, and access any of the plating units 20 a to 20 d, the bevel etching units 21 a, 21 b and the cleaning units 22 a, 22 b to load and unload the wafer W.

[0082] A basic wafer transport route and a basic process sequence are as follows. First, an untreated wafer W is unloaded from one of the cassettes Cw, then transported to the front of one of the plating units 20 a to 20 d, and loaded into the plating unit 20 a to 20 d by the robot body 18 so as to be subjected to the plating process. In turn, the wafer W subjected to the plating process is unloaded from the plating unit 20 a to 20 d, and loaded into one of the bevel etching units 21 a, 21 b by the robot body 18 so as to be subjected to the bevel etching process.

[0083] Subsequently, the wafer W subjected to the bevel etching process is unloaded from the bevel etching unit 21 a, 21 b, then transported along the second transport path 15, and loaded into one of the cleaning units 22 a, 22 b by the robot body 18 so as to be subjected to the cleaning process.

[0084] Further, the wafer W subjected to the cleaning process is unloaded from the cleaning unit 22 a, 22 b and then transported along the second transport path 15 toward the first transport path 14 by the robot body 18. Upon reaching the first transport path 14, the robot body 18 starts moving along the transport path 14 to the front of a cassette Cw placed on one of the cassette stages 16, and loads the wafer W on the cassette C.

[0085] The wafer treating section 1 is enclosed in an enclosure so as not to be affected by an external environment.

[0086] FIGS. 3(a) , 3(b) and 3(c) are a schematic plan view, a schematic side view and a schematic front view, respectively, for explaining the construction of the robot body 18.

[0087] The robot body 18 includes a base 23, a vertical articulated arm 24 attached to the base 23, a pivotal driving mechanism 25 attached to the vertical articulated arm 24, and a substrate holder 26 to be driven pivotally about a vertical pivot axis V0 by the pivotal driving mechanism 25 (only the substrate holder 26 is shown in FIG. 3(a)).

[0088] The substrate holder 26 includes a body 40 having a flat top, and a pair of retractable arms 41, 42 provided on the flat top of the body 40. A retractable driving mechanism (not shown) for horizontally advancing and retracting the pair of retractable arms 41, 42 is incorporated in the body 40.

[0089] The retractable arms 41 and 42 respectively include first arm portions 41 a and 42 a, second arm portions 41 b and 42 b, and substrate holder hands (effecters) 41 c and 42 c. The body 40 has a generally round shape as seen in plan, and the first arm portions 41 a, 42 a are attached to a peripheral edge portion of the body 40 pivotally about vertical pivot axes thereof. The first arm portions 41 a, 42 a are driven pivotally about the pivot axes by the retractable driving mechanism provided in the body 40.

[0090] The retractable arms 41, 42 each constitute a so-called scholar robot, which is operative so that the second arm portion 41 b, 42 b is pivoted about a vertical pivot axis thereof in synchronization with the pivoting of the first arm portion 41 a, 42 a. Thus, the first arm portion 41 a, 42 a and the second arm portion 41 b, 42 b of the retractable arm 41, 42 are stretched and unstretched so as to advance and retract the substrate holder hand 41 c, 42 c.

[0091] When the retractable arms 41, 42 are in an unstretched state, the substrate holder hands 41 c, 42 c are kept in vertically overlapped relation (FIG. 3(a)). Therefore, the substrate holder hand 41 c of the retractable arm 41 has a bent shape for prevention of interference with the substrate holder hand 42 c of the retractable arm 42 (FIG. 3(b)).

[0092] A first arm 24 a is attached to the base 23 pivotally about a horizontal pivot axis H1 at one end thereof. A second arm 24 b is attached to the other end of the first arm 24 a pivotally about a horizontal pivot axis H2 at one end thereof. The pivotal driving mechanism 25 is attached to the other end of the second arm 24 b pivotally about a horizontal pivot axis H3. The pivot axes H1, H2 and H3 are parallel to each other.

[0093] A motor 27 for pivoting the first arm 24 a is provided n the base 23, and a motor 28 for pivotally driving the second arm 24 b is provided in a coupling between the first arm 24 a and the second arm 24 b. The motor 28 is rotatable in synchronization with the motor 27. A driving force transmission mechanism (not shown) for transmitting a driving force from the motor 28 to the pivotal driving mechanism 25 is incorporated in the second arm 24 b. Thus, the pivotal driving mechanism 25 can constantly hold the substrate holder 26 in the same attitude (e.g., in such an attitude as to hold the wafer W horizontally) , even if the first arm 24 a and the second arm 24 b are pivoted.

[0094] A motor (not shown) is incorporated in the pivotal driving mechanism 25. The pivotal driving mechanism 25 receives a driving force from this motor to pivotally drive the substrate holder 26 about the vertical pivot axis V0.

[0095] With this arrangement, the transport robot TR can move the substrate holder hands 41 c, 42 c horizontally and vertically within a range hatched in FIG. 3(c).

[0096] When the robot body 18 accesses the cassette C (the cassette Cw or the cassette Cd) placed on one of the cassette stages 16 (see FIG. 2), the robot body 18 is moved to ends of the transport guide rails 17 on the side of the first transport path 14 by the transport controller 29. In this state, the substrate holder 26 is brought into opposed relation to the cassette C on the cassette stage 16 by the operation of the vertical articulated arm 24. That is, the substrate holder 26 can be moved along the first transport path 14, while the base 23 is kept located on the transport guide rails 17.

[0097] Then, the retractable arm 41, 42 is brought into opposed relation to the cassette C by the operation of the pivotal driving mechanism 25, and caused to access the cassette C by the retractable driving mechanism not shown for loading and unloading the wafer W with respect to the cassette C. When the wafer W is transferred between the cassette C and the retractable arm 41, 42, the substrate holder 26 is slightly moved up or down by the operation of the vertical articulated arm 24.

[0098] When the robot body 18 accesses any of the plating units 20 a to 20 d, the bevel etching units 21 a, 21 b and the cleaning units 22 a, 22 b (see FIG. 2) , the robot body 18 is moved to the front of the corresponding unit on the transport guide rails 17 by a movement mechanism not shown. In this state, the substrate holder 26 is moved up or down to the height of a substrate loading/unloading port of the unit by the operation of the vertical articulated arm 24, and the retractable arm 41, 42 is brought into opposed relation to the unit by pivoting the substrate holder 26 by means of the pivotal driving mechanism 25.

[0099] In this state, the retractable arm 41, 42 is caused to access the unit by the retractable driving mechanism for the loading and unloading of the wafer W. When the wafer W is transferred between the unit and the retractable arm 41, 42, the substrate holder 26 is slightly moved up or down by the operation of the vertical articulated arm 24.

[0100] With this arrangement, the cassette C, the plating units 20 a to 20 d, the bevel etching units 21 a, 21 b and the cleaning units 22 a, 22 b can be accessed by the single robot body 18 for the loading and unloading of the wafer W and the dummy wafer D.

[0101] The wafer W subjected to the plating process in the plating unit 20 a to 20 d (hereinafter referred to as “entire-surface-plated wafer”) has a copper film formed on the entire surface thereof including the peripheral edge thereof by the plating, before the wafer W is subjected to the bevel etching process in the bevel etching unit 21 a, 21 b. Therefore, the substrate holder hand 41 c, 42 c which holds the entire-surface-plated wafer is contaminated with copper. Therefore, it is preferred that one of the substrate holder hands 41 c and 42 c is dedicated to holding the entire-surface-plated wafer. Thus, the contamination with copper is prevented from spreading via the substrate holder hand 41 c or 42 c.

[0102] FIGS. 4(a) and 4(b) are a schematic plan view and a schematic side view, respectively, of the cassette stage 16 on which the cassette C is placed.

[0103] The cassette stage 16 includes a planar cassette base 50 for receiving thereon the cassette C. The cassette base 50 has a generally square shape as seen in plan. The cassette C has a generally square shape having a smaller size than the cassette base 50 as seen in plan, and has a wafer loading/unloading opening Ce provided on one lateral side thereof.

[0104] The cassette base 50 has cassette guides 51 provided on one surface thereof in association with four corners of the cassette C as seen in plan. Therefore, the cassette C can be located in position on the cassette base 50 with its corners in contact with the cassette guides 51. With the cassette C located in position on the cassette base 50, the wafer loading/unloading opening Ce faces toward the first transport path 14 (see FIG. 2).

[0105] A light emitting element 52 a and a light receiving element 52 b are respectively provided at generally middle points on opposite edges of the cassette base 50 (excluding an edge having the wafer loading/unloading opening Ce) on the surface of the cassette base 50. The light emitting element 52 a and the light receiving element 52 b constitute a transmissive photosensor 52. When no cassette C is present on the cassette base 50, light emitted from the light emitting element 52 a is received by the light receiving element 52 b. When the cassette C is present on the cassette base 50, the light emitted from the light emitting element 52 a is blocked by the cassette C and does not reach the light receiving element 52 b. Thus, a judgment can be made on the presence or absence of the cassette C on the cassette base 50.

[0106] There is no difference in construction between the cassette Cw accommodating the wafer W and the cassette Cd accommodating the dummy wafer D. Further, there is no difference in construction between the cassette stage 16 on which the cassette Cw is placed and the cassette stage 16 on which the cassette Cd is placed.

[0107]FIG. 5 is a schematic front view illustrating the construction of the plating section 12.

[0108] The plating section 12 includes a plurality of plating units (the four plating units 20 a to 20 d in this embodiment) for the plating of the wafer W, and a plating liquid container 55 for containing the plating liquid. The plating units 20 a to 20 d respectively include plating cups 56 a to 56 d for containing the plating liquid, and wafer holding/rotating mechanisms (treatment heads) 74 a to 74 d to be located above the plating cups 56 a to 56 d.

[0109] The plating liquid container 55 is capable of containing the plating liquid in a much greater amount than the plating cups 56 a to 56 d (e.g., 20 times the total volume of the plating cups 56 a to 56 d) . Since a great amount of the plating liquid can be stored in the plating liquid container 55, the total amount of the plating liquid to be used in the plating section 12 can be increased. Thus, variations in the composition of the plating liquid can be reduced during the plating process.

[0110] The plating liquid transport pipe P12 a for transporting the plating liquid to the major constituent managing section 2 is connected to the bottom of the plating liquid container 55 in communication with the plating liquid container 55. The plating liquid transport pipe P12 b for introducing the plating liquid transported from the major constituent managing section 2 into the plating liquid container 55, the plating liquid transport pipe P13 a for transporting the plating liquid to the minor constituent managing section 3, and the plating liquid transport pipe P13 b for introducing the plating liquid transported from the minor constituent managing section 3 into the plating liquid container 55 are introduced into the plating liquid container 55 from the top of the plating liquid container 55. The plating liquid transport pipes P12 b, P13 a, P13 b extend to a depth at which open ends thereof are submerged in the plating liquid in the plating liquid container 55.

[0111] The plating cups 56 a to 56 d are located at a higher position than the plating liquid container 55. A liquid supply pipe 57 extends from the bottom of the plating liquid container 55, and is branched into four branch liquid supply pipes 58 a to 58 d. The branch liquid supply pipes 58 a to 58 d extend upward to be respectively connected to bottom center portions of the plating cups 56 a to 56 d in communication with the plating cups 56 a to 56 d.

[0112] Pumps P1 to P4, filters 59 a to 59 d and flow meters 60 a to 60 d are provided in this order from a lower side to an upper side in the respective branch liquid supply pipes 58 a to 58 d. The pumps P1 to P4 are respectively capable of pumping the plating liquid from the plating liquid container 55 to the plating cups 56 a to 56 d. The operations of the pumps P1 to P4 are controlled by the system controller 155. The filters 59 a to 59 d are capable of removing particles (contaminants) from the plating liquid. Signals indicative of the flow rates of the plating liquid is outputted from the flow meters 60 a to 60 d, and inputted to the system controller 155.

[0113] The plating cups 56 a to 56 d respectively include cylindrical plating vessels (liquid containing portions) 61 a to 61 d provided inwardly thereof, and recovery vessels 62 a to 62 d surrounding the plating vessels 61 a to 61 d. The branch liquid supply pipes 58 a to 58 d are connected in communication with the plating vessels 61 a to 61 d. Branch return pipes 63 a to 63 d respectively extend from bottom portions of the recovery vessels 62 a to 62 d. The branch return pipes 63 a to 63 d are connected in communication with a return pipe 64, which extends into the plating liquid container 55.

[0114] With the aforesaid arrangement, the plating liquid is supplied, for example, to the plating vessel 61 a from the plating liquid container 55 through the liquid supply pipe 57 and the branch liquid supply pipe 58 a by operating the pump P1. The plating liquid overflows from the top of the plating vessel 61 a, and is fed back into the plating liquid container 55 from the recovery vessel 62 a through the branch return pipe 63 a and the return pipe 64 by gravity. That is, the plating liquid is circulated through the plating liquid container 55 and the plating cup 56 a.

[0115] Similarly, the plating liquid is circulated through the plating liquid container 55 and the plating cup 56 b, 56 c or 56 d by operating the pump P2, P3 or P4. When the plating process is performed in any of the plating units 20 a to 20 d, the plating liquid is circulated through the plating cup 56 a to 56 d of the corresponding plating unit 20 a to 20 d and the plating liquid container 55. Thus, the plating liquid container 55 is shared by the four plating units 20 a to 20 d.

[0116] One end of a bypass pipe 65 is connected to the branch liquid supply pipe 58 a between the pump P1 and the filter 59 a. The other end of the bypass pipe 65 is introduced into the plating liquid container 55. Absorptiometers 66A, 66B for measuring absorbances of the plating liquid at specific wavelengths of light are provided in the bypass pipe 65. The absorptiometer 66A is provided for determining the concentration of copper in the plating liquid, while the absorptiometer 66B is provided for determining the concentration of iron in the plating liquid.

[0117] When the pump P1 is operated to circulate the plating liquid through the plating liquid container 55 and the plating cup 56 a, a part of the plating liquid flowing through the branch liquid supply pipe 58 a flows into the bypass pipe 65 due to a pressure loss by the filter 59 a. That is, the plating liquid can be introduced into the bypass pipe 65 without provision of a dedicated pump in the bypass pipe 65.

[0118] The absorptiometers 66A, 66B each include a cell 67A, 67B composed of a transparent material, and a light emitting section 68A, 68B and a light receiving section 69A, 69B disposed in opposed relation with the cell 67A, 67B interposed therebetween. The light emitting sections 68A and 68B are respectively capable of emitting light beams having specific wavelengths corresponding to absorption spectra of copper and iron (e.g., 780 nm for copper). The light receiving sections 69A and 69B are respectively capable of measuring the intensities of the light beams emitted from the light emitting sections 68A and 68B and transmitted through the plating liquid in the cells 67A and 67B. The absorbances of the plating liquid are determined on the basis of the light intensities. Signals indicative of the absorbances are outputted from the absorptiometers 66A, 66B, and inputted to the system controller 155.

[0119] A temperature sensor 70 and an electromagnetic conductivity meter 71 are attached to a side wall of the plating liquid container 55. The temperature sensor 70 and the electromagnetic conductivity meter 71 are located at a height lower than the surface level of the plating liquid contained in the plating liquid container 55. Detectors of the temperature sensor 70 and the electromagnetic conductivity meter 71 project into the plating liquid container 55, and are respectively adapted to measure the temperature and electrical conductivity of the plating liquid. Output signals of the temperature sensor 70 and the electromagnetic conductivity meter 71 are inputted to the system controller 155.

[0120] The concentrations of copper and iron in the plating liquid can be determined by measuring the absorbances of the plating liquid at the specific wavelengths of light. An explanation will be given to how to determine the copper concentration on the basis of the absorbance of the plating liquid.

[0121] For the determination of the copper concentration of the plating liquid, a relationship between the copper concentration and the absorbance is preliminarily determined. First, plural plating liquid samples having different copper concentrations are prepared. Copper sulfate is added as a copper source for the preparation of the plating liquid samples. The plating liquid samples each have substantially the same composition as the plating liquid actually used for the plating process, except that the copper concentrations thereof are different. The absorbances of the plating liquid samples are measured by the absorptiometer 66A. Thus, the relationship between the copper concentration and the absorbance (copper calibration line) is determined on the basis of the known copper concentrations and the measured absorbances of the plating liquid samples as shown in FIG. 6.

[0122] For the determination of an unknown copper concentration of the plating liquid, the absorbance of the plating liquid is measured by the absorptiometer 66A. Then, the copper concentration is determined on the basis of the measured absorbance and the copper calibration line.

[0123] Similarly, a relationship between the iron concentration and the absorbance (iron calibration line) is preliminarily determined on the basis of known iron concentrations and measured absorbances of plating liquid samples, and the concentration of iron in the plating liquid is determined on the basis of the absorbance of the plating liquid measured by the absorptiometer 66B and the iron calibration line.

[0124] The system controller 155 includes a storage device storing therein data of the copper calibration line and the iron calibration line. The system controller 155 is capable of determining the copper concentration on the basis of the output signal of the absorptiometer 66A and the data of the copper calibration line, and determining the iron concentration on the basis of the output signal of the absorptiometer 66B and the data of the iron calibration line.

[0125] An ultrasonic level meter 72 is provided above the plating liquid container 55. The ultrasonic level meter 72 is capable of detecting the surface level of the plating liquid in the plating liquid container 55. An output signal of the ultrasonic level meter 72 is inputted to the system controller 155. A capacitive level meter may be employed instead of the ultrasonic level meter 72.

[0126] The plating liquid container 55, the liquid supply pipe 57, the branch liquid supply pipes 58 a to 58 d, the branch return pipes 63 a to 63 d and the return pipe 64 are disposed in a pipe chamber 73 virtually air-tightly enclosed by the enclosure and partition walls of the wafer treating section 1. The pipe chamber 73 has an air outlet port 32, which is connected to an air outlet duct 34. The other end of the air outlet duct 34 is connected to an in-plant exhauster system line. Air possibly exposed to the plating liquid and the like in the plating section 12 is forcibly exhausted out of the clean room. During the forcible air exhaustion, the internal pressure of the pipe chamber 73 is kept at a negative pressure.

[0127]FIG. 7 is a schematic sectional view illustrating the common construction of the plating units 20 a to 20 d. The wafer holding/rotating mechanisms 74 a to 74 d are each supported by an inversion base 181. An inversion driving section 43 is connected to one end of the inversion base 181.

[0128] The inversion driving section 43 includes a column-shaped vertical base 182 extending vertically, a rotary actuator 183 attached to the vertical base 182 and having a rotation shaft perpendicular to the vertical base 182, and a toothed pulley 184 attached to the rotation shaft of the rotary actuator 183, a toothed pulley 185 attached to a shaft extending parallel to the shaft of the rotary actuator 183 and supported rotatably by the vertical base 182, and a timing belt 186 stretched between the toothed pulley 184 and the toothed pulley 185 for transmitting a rotation force of the rotary actuator 183.

[0129] The rotary actuator 183 may be, for example, pneumatically driven. The inversion base 181 is attached to the vicinity of the shaft of the toothed pulley 185 perpendicularly to the toothed pulley 185. The inversion base 181 and the wafer holding/rotating mechanism 74 a to 74 d supported by the inversion base 181 can be pivoted (inverted) about the horizontal shaft as indicated by an arrow a in FIG. 7 by a pivotal driving force of the rotary actuator 183. Thus, the wafer W held by the wafer holding/rotating mechanism 74 a to 74 d can face upward or downward toward the plating cup 56 a to 56 d.

[0130] The vertical base 182 is coupled to a lift mechanism 44. The lift mechanism 44 includes a first motor 44 a having a vertical rotation shaft, a ball thread 44 b attached to the first motor 44 a coaxially with the rotation shaft of the first motor 44 a, and a vertical column-shaped guide 44 c. The first motor 44 a maybe, for example, a servo motor. A support member 182 a having an internal thread portion is provided in threading engagement with the ball thread 44 b in the vicinity of a lower end of the vertical base 182. The guide 44 c vertically guides the vertical base 182 while preventing the vertical base 182 from rotating about the axis of the ball thread 44 b.

[0131] With this arrangement, the vertical base 182 can be moved vertically by rotating the first motor 44 a. Therefore, the inversion base 181 coupled to the vertical base 182 and the wafer holding/rotating mechanism 74 a to 74 d supported by the inversion base 181 can vertically be moved up and down (in directions indicated by an arrow b in FIG. 7).

[0132] The wafer holding/rotating mechanism 74 a to 74 d includes a rotary pipe 77 and a disk-shaped spin base 78 attached to one end of the rotary pipe 77 perpendicularly to the rotary pipe 77. The rotary pipe 77 is supported rotatably about its axis by the inversion base 181.

[0133] A plurality of wafer transfer pins 84 are provided on a surface of the spin base 78 opposite from the rotary pipe 77 between the center and the peripheral edge of the spin base 78. A plurality of support posts (e.g., four support posts) 79 are provided in a peripheral edge portion on the surface of the spin base 78 opposite from the rotary pipe 77. An annular cathode ring 80 is attached to distal ends of the support posts 79. The support posts 79 have a greater length than the wafer transfer pins 84.

[0134] The cathode ring 80 has an abutment portion 80 a projecting toward the center of the cathode ring 80. The abutment portion 80 a has an inner diameter slightly smaller than the diameter of the wafer W. The cathode ring 80 further has a projection 80 p projecting opposite from the support posts 79.

[0135] A susceptor 81 is provided coaxially with the rotary pipe 77. The susceptor 81 includes a support shaft 81 b extending through the rotary pipe 77, and a disk-shaped wafer back side press plate 81 a attached to an end of the support shaft 81 b (on the side of the cathode ring 80) perpendicularly to the support shaft 81 b. The wafer back side press plate 81 a is surrounded by the plurality of support posts 79. The wafer back side press plate 81 a has a slightly smaller diameter than the wafer W. An end portion of the support shaft 81 b opposite from the wafer back side press plate 81 a projects out of the rotary pipe 77.

[0136] The susceptor 81 is coupled to a susceptor movement mechanism 46. The susceptor movement mechanism 46 includes an air cylinder 46 a attached to the inversion base 181, and a transmission member 46 b which couples a piston of the air cylinder 46 a to the support shaft 81 b. The transmission member 46 b is fixed to the end portion of the support shaft 81 b projecting out of the rotary pipe 77 opposite from the wafer back side press plate 81 a. The susceptor 81 can be moved along the center axis of the rotary pipe 77 by driving the air cylinder 46 a.

[0137] The wafer back side press plate 81 a is formed with holes in association with the wafer transfer pins 84. Thus, the wafer transfer pins 84 are inserted into the holes of the wafer back side press plate 81 a, as the susceptor 81 is moved with respect to the rotary pipe 77. With the aforesaid arrangement, the wafer W can be held by the abutment portion 80 a of the cathode ring 80 and the wafer back side press plate 81 a.

[0138] A rotative driving mechanism 45 for rotating the rotary pipe 77 about its axis is coupled to the rotary pipe 77. The rotative driving mechanism 45 includes a second motor 45 a provided on the inversion base 181 and having a rotation shaft parallel to the axis of the rotary pipe 77, a toothed pulley 45 b fixed to the rotation shaft of the second motor 45 a, a toothed pulley 45 c provided around the rotary pipe 77, and a timing belt 45 d stretched between the toothed pulley 45 b and the toothed pulley 45 c for transmitting a rotation force of the second motor 45 a.

[0139] The rotary pipe 77 can be rotated about its axis (in a direction indicated by an arrow c in FIG. 7) by a rotative driving force of the second motor 45 a. The second motor 45 a may be, for example, a servo motor. The rotation of the rotary pipe 77 is transmitted to the susceptor 81, while permitting the susceptor 81 to move axially of the rotary pipe 77. Therefore, the rotary pipe 77 and the susceptor 81 are rotated together. Thus, the wafer W held by the abutment portion 80 a of the cathode ring 80 and the wafer back side press plate 81 a can be rotated.

[0140] In the plating process, the wafer holding/rotating mechanism 74 a to 74 d is moved down by the lift mechanism 44 with the wafer W thus held as facing downward, and a lower surface of the wafer W is brought into contact with the plating liquid filled in the plating vessel 61 a to 61 d.

[0141]FIG. 8 is a schematic sectional view illustrating a portion around the wafer W as observed in the plating process.

[0142] Referring to FIGS. 7 to 8, a continuous fluid channel 81 c is provided in the support shaft 81 b and the wafer back side press plate 81 a. The fluid channel 81 c is provided as a single fluid channel extending through the support shaft 81 b along the center axis of the support shaft 81 b, and branched into a plurality of branch channels in the wafer back side press plate 81 a. The branch channels extend from the center to the peripheral edge of the wafer back side press plate 81 a, and open in the peripheral edge of the wafer back side press plate 81 a.

[0143] A rotary joint 191 is attached to the end of the support shaft 81 b opposite from the wafer back side press plate 81 a. One end of a supply pipe 203 and one end of a leak pipe 204 are connected to the rotary joint 191. The other end of the supply pipe 203 is branched into a cathode cleaning liquid pipe 201 and a nitrogen gas pipe 202.

[0144] The cathode cleaning liquid pipe 201 is connected to a cathode cleaning liquid supply source, and the nitrogen gas pipe 202 is connected to a nitrogen gas supply source. A valve 201V is provided in the cathode cleaning liquid pipe 201, so that a cathode cleaning liquid (e.g., deionized water) can be supplied into the rotary joint 191 by opening the valve 201V. A valve 202V is provided in the nitrogen gas pipe 202, so that nitrogen gas can be supplied into the rotary joint 191 by opening the valve 202V.

[0145] Even during the rotation of the susceptor 81, the cathode cleaning liquid and nitrogen gas can be supplied into the fluid channel 81 c from the cathode cleaning liquid supply source and the nitrogen gas supply source on the side of a stationary system through the rotary joint 191.

[0146] A part of the cathode cleaning liquid supplied from the supply pipe 203 is drained through the leak pipe 204. Particles generated around slidable members in the rotary joint 191 are washed away into the leak pipe 204 by the cathode cleaning liquid, thus the particles are prevented from flowing into the fluid channel 81 c.

[0147] The cathode ring 80 includes an upper ring 80 u, a conduction plate 80 c and a base ring 80 b arranged in this order from the side of the spin base 78. The upper ring 80 u, the conduction plate 80 c and the base ring 80 b each have a ring shape. The base ring 80 b is composed of an inelastic material. The conduction plate 80 c is covered with the upper ring 80 u and the base ring 80 b. The conduction plate 80 c is electrically conductive. The conduction plate 80 c imparts the entire cathode ring 80 with a sufficient strength.

[0148] The base ring 80 b is provided with the abutment portion 80 a. The abutment portion 80 a has a sealing surface 80 s to be brought into contact with the wafer W in opposed relation to a peripheral edge portion of the wafer back side press plate 81 a.

[0149] A plurality of fluid channels 80 f are provided in the base ring 80 b as extending radially through the base ring 80 b. Where the wafer back side press plate 81 a and the cathode ring 80 are located in position in the plating process, the fluid channels 80 f are located at a lower position than the branch channels of the fluid channel 81 c. A multiplicity of notches are provided in an inner peripheral portion of the upper ring 80 u, whereby the cathode cleaning liquid flowing out of the branch channels of the fluid channel 81 c opening in the periphery of the wafer back side press plate 81 a can be introduced into the fluid channels 80 f in the plating process.

[0150] A cathode 83 is disposed in the fluid channels 80 f. The cathode 83 is disposed within substantially the same plane as the sealing surface 80 s outwardly of the abutment portion 80 a with respect to the center of the cathode ring 80.

[0151] The cathode 83 is composed of a spring stainless steel having a thickness of about 0.1 mm, and has a surface plated with platinum. This prevents formation of an oxide film on the surface of the cathode 83, and prevents dissolution of the cathode 83 even if a reverse electric field is applied to the cathode 83. If the platinum film of the cathode 83 is too thin, the service life of the platinum film is reduced due to abrasion. If the platinum film of the cathode 83 is too thick, the film is liable to be cracked when the cathode 83 behaves resiliently. In view of these, the thickness of the platinum film of the cathode 83 is preferably about 0.01 μm to about 2 μm.

[0152] The cathode 83 has a multiplicity of contact portions 83 c arranged like a comb circumferentially of the cathode ring 80 as extending toward the center of the cathode ring 80. The contact portions 83 c are each bent at an angle θ of 5 to 60 degrees with their distal ends raised toward the wafer back side press plate 81 a. The bent contact portions 83 c are restricted by the upper ring 80 u.

[0153] The cathode 83 is brought into resilient contact with a peripheral edge portion of the wafer W or the dummy wafer D, while the wafer W or the dummy wafer D is held between the abutment portion 80 a and the wafer back side press plate 81 a. That is, the contact portions 83 c can be kept in contact with the wafer W or the dummy wafer D at a predetermined contact pressure.

[0154] An electrically-conductive ring-shaped electrode press 80 d is disposed between the base ring 80 b and the upper ring 80 u in the vicinity of the conduction plate 80 c. The base ring 80 b has a groove, in which a coil spring 80e is housed. The cathode 83 is fixed to the electrode press 80 d for electrical connection, and the electrode press 80 d and the conduction plate 80 c are kept in resilient contact with each other by the coil spring 80 e for electrical connection. Thus, the electrical connection is maintained between the electrode press 80 d and the conduction plate 80 c, even if the base ring 80 b is pressed to be warped by the wafer back side press plate 81 a.

[0155] The support posts 79 are electrically conductive, and extend through the upper ring 80 u so as to be electrically connected to the conduction plate 80 c. O-rings 80 r are provided between the support posts 79 and the upper ring 80 u (around the support posts 79) , between the upper ring 80 u and the base ring 80 b around the conduction plate 80 c, between the upper ring 80 u and the electrode press 80 d (along the inner periphery of the electrode press 80 d) ,and between the base ring 80 b and the electrode press 80 d (along the outer periphery of the electrode press 80 d) . This prevents the plating liquid from intruding into the cathode ring 80. When the cathode ring 80 is detached from the spin base 78 for cleaning thereof, the cathode ring 80 can be immersed in the cleaning liquid without the need for disassembling the cathode ring 80 for cleaning thereof.

[0156] A conduction line 198 is provided within the spin base 78 and the rotary pipe 77. An electrically conductive coupling plate 78 j is attached to the peripheral portion of the surface of the spin base 78 facing toward the cathode ring 80 via an insulative plate 78 i. The conduction line 198 is electrically connected to the coupling plate 78 j via a conduction stud 78 s extending through the insulative plate 78 i.

[0157] An electrically conductive coupling member 79 j is attached to ends of the support posts 79 opposite from the conduction plate 80 c. The coupling member 78 j has a positioning pin 78 p, while the coupling member 79 j is formed with a positioning hole 79 h. The coupling member 78 j and the coupling member 79 j are coupled to each other with the positioning pin 78 p fitted in the positioning hole 79 h. Thus, the cathode ring 80 is fixed to the spin base 78 in proper positional relationship. Even when the cathode ring 80 is rotated at a high speed, there is no possibility that the cathode ring 80 is offset. When the cathode ring 80 is detached from the spin base 78 by decoupling the coupling members 78 j, 79 j, the support posts 79 serve as handles of the cathode ring 80.

[0158] With the aforesaid arrangement, the cathode 83 is electrically connected to the conduction line 198.

[0159] An electrical connection mechanism 192 is provided between a plating power source 82 and the conduction line 198, so that electrical connection can be established between the conduction line 198 rotated together with the cathode ring 80 and the plating power source 82 provided on the side of the stationary system.

[0160] The electrical connection mechanism 192 includes an electrically conductive pulley 193 fitted around an end portion of the rotary pipe 77 opposite from the spin base 78, an electrically conductive rotary shaft 194 rotatably attached to the inversion base 181 in parallel relation to the rotary pipe 77, an electrically conductive pulley 195 fitted around the rotary shaft 194, an electrically conductive belt 196 stretched between the pulley 193 and the pulley 195, and a slip ring 197 attached to a distal end of the rotary shaft 194.

[0161] The pulleys 193, 195 each have a surface plated with gold, for example, which is kept in contact with the belt 196. The belt 196 may be a steel belt having a surface plated with gold, for example. In this case, the electrical resistance between the pulley 193 and the pulley 195 can be reduced. The pulley 193 and the pulley 195 are mechanically connected to each other by the belt 196. When the rotary pipe 77 is rotated by the rotative driving mechanism 45, the rotative driving force is transmitted to the rotary shaft 194 via the pulley 193, the belt 196 and the pulley 195, whereby the rotary shaft 194 is rotated. Even during the rotation of the rotary pipe 77 and the rotary shaft 194, the electrical connection between the pulleys 193 and 195 is maintained.

[0162] The slip ring 197 is of a non-slidable type, which establishes the electrical connection between a rotary component and a stationary component, for example, via mercury. The slip ring 197 includes a stationary terminal and a rotary terminal for electrical connection between the stationary system and the rotary system.

[0163] The conduction line 198 is electrically connected to the pulley 193. The pulley 193 is electrically isolated from the rotary pipe 77. Further, the pulley 195 is electrically connected to the rotary shaft 194. The rotary shaft 194 is electrically connected to the rotary terminal of the slip ring 197. The stationary terminal of the slip ring 197 is electrically connected to the plating power source 82 via a conduction line 199A.

[0164] With the aforesaid arrangement, the cathode 83 and the plating power source 82 are electrically connected to each other, even when the rotary pipe 77 and the rotary shaft 194 are rotated. Where the belt 196 is stretched between the pulleys 193 and 195 with a sufficiently great tensile force, the belt 196 can be brought into non-sliding contact with the pulleys 193 and 195. Since the slip ring 197 is of a non-slidable type, there is no sliding contact between the plating power source 82 and the cathode 83. Therefore, the electrical connection can properly be established between the plating power source 82 and the cathode 83, while a noise attributable to the sliding contact such as a so-called brush noise is suppressed.

[0165] Since the rotary joint 191 and the slip ring 197 are respectively attached to the ends of the support shaft 81 b and the rotary shaft 194, the replacement thereof is easy. That is, when the rotary joint 191 or the slip ring 197 is replaced, interference between the rotary joint 191 and the slip ring 197 can be avoided, which may otherwise occur where the rotary joint 191 and the slip ring 197 are both attached to the support shaft 81 b or the rotary pipe 77.

[0166] Since the rotary joint 191 and the slip ring 197 are respectively attached to the ends of the support shaft 81 b and the rotary shaft 194, the lengths of the support shaft 81 b (rotary pipe 77) and the rotary shaft 194 can be reduced. Therefore, the size of the wafer holding/rotating mechanism 74 a to 74 d as measured axially of the support shaft 81 b can be reduced, so that the wafer holding/rotating mechanism 74 a to 74 d can be inverted with a reduced turning radius.

[0167] The operations of the plating power source 82, the inversion driving section 43 (rotary actuator 183), the lift mechanism 44 (first motor 44 a) , the rotative driving mechanism 45 (second motor 45 a) and the susceptor movement mechanism 46 (air cylinder 46 a), and the opening and closing of the valves 201V, 202V are controlled by the system controller 155.

[0168] Next, an explanation will be given to the construction of the plating cup 56 a to 56 d. The plating vessel 61 a to 61 d has a cylindrical side wall having an inner diameter virtually equal to the outer diameters of the wafer W and the dummy wafer D. A plating liquid supply port 54 is provided in a bottom center portion of the plating vessel 61 a to 61 d. The branch liquid supply pipe 58 a to 58 d is connected to the plating liquid supply port 54 as slightly projecting into the plating vessel 61 a to 61 d. A semispherical shower head 75 having a multiplicity of holes is attached to an end of the branch liquid supply pipe 58 a to 58 d located in the plating vessel 61 a to 61 d. The plating liquid is diffusively introduced in various directions (at various angles) into the plating vessel 61 a to 61 d through the shower head 75.

[0169] A three-dimensional filter including a plurality of fluororesin mesh members 49 stacked one on another is provided in an upper portion of the plating vessel 61 a to 61 d. The mesh members 49 each have a round plan shape having an outer diameter virtually equal to the inner diameter of the plating vessel 61 a to 61 d. The plurality of stacked mesh members 49 generally entirely cover the plating vessel 61 a to 61 d as viewed in plan. The plating liquid supplied upward from the lower side of the plating vessel 61 a to 61 d is rectified by the mesh members 49.

[0170] A mesh anode 76 is provided at a level about one fourth the depth of the plating vessel 61 a to 61 d from the bottom in the plating vessel 61 a to 61 d (between the shower head 75 and the mesh members 49) . The anode 76 is a titanium mesh member coated with iridium oxide, and is insoluble in the plating liquid. Since the anode 76 is mesh-shaped, the flow of the plating liquid is not hindered by the anode 76.

[0171] The anode 76 has a round plan shape having an outer diameter virtually equal to the inner diameter of the plating vessel 61 a to 61 d, and generally entirely covers the plating vessel 61 a to 61 d as viewed in plan. The anode 76 is connected to the plating power source 82 via a conduction line 199B.

[0172] A plating liquid outlet port 53 is provided in the bottom of the plating liquid recovery vessel 62 a to 62 d. The branch return pipe 63 a to 63 d is connected in communication with the plating liquid recovery vessel 62 a to 62 d via the plating liquid outlet port 53.

[0173] An upper edge portion of the plating vessel 61 a to 61 d has a reduced wall thickness with its outer circumferential portion cut away, and is complementary in configuration to a portion of the cathode ring 80 (base ring 80 b) which is brought into opposed relation to the upper edge portion of the plating vessel 61 a to 61 d in the plating process. This prevents the interference between the plating vessel 61 a to 61 d and the cathode ring 80 in the plating process (see FIG. 8). In the plating process, the projection 80 p of the cathode ring 80 is inserted in an upper portion of the recovery vessel 62 a to 62 d.

[0174] A cathode cleaning liquid collection vessel 210 is provided around the plating liquid recovery vessel 62 a to 62 d for collecting the cathode cleaning liquid after cleaning the cathode 83. That is, the plating cup 56 a to 56 d has a triple structure having the plating vessel 61 a to 61 d, the plating liquid recovery vessel 62 a to 62 d and the cathode cleaning liquid collection vessel 210 arranged in this order from the inside to the outside. A liquid drain pipe 215 is connected to the bottom of the cathode cleaning liquid collection vessel 210, so that liquid can be drained from the cathode cleaning liquid collection vessel 210.

[0175] A liquid trap 211 is also connected to the bottom of the cathode cleaning liquid collection vessel 210, so that a part of the liquid (the cathode cleaning liquid and the like) flowing into the cathode cleaning liquid collection vessel 210 can be trapped in the liquid trap 211. A conductivity meter 212 is inserted in the liquid trap 211. Thus, the electrical conductivity of the liquid trapped in the liquid trap 211 can be measured. An output signal of the conductivity meter 212 is inputted to the system controller 155.

[0176] An overflow pipe 213 is connected to an upper edge portion of a side wall of the liquid trap 211. When the surface level of the liquid in the liquid trap 211 rises to reach the height of the overflow pipe 213, the liquid overflows from the overflow pipe 213. A drain pipe 214 is connected to the bottom of the liquid trap 211. Therefore, when the plating unit 20 a to 20 d is not in use, the liquid can be drained from the liquid trap 211.

[0177] When the plating process is performed in the plating section 12, the system controller 155 first controls the inversion driving section 43 to invert any of the wafer holding/rotating mechanisms 74 a to 74 d (herein assumed to be the wafer holding/rotating mechanism 74 a) with the wafer back side press plate 81 a thereof facing upward. Further, the system controller 155 controls the susceptor movement mechanism 46 to move the wafer back side press plate 81 a toward the rotary pipe 77, so that the wafer transfer pins 84 project out through the wafer back side press plate 81 a. This state is shown in FIG. 9.

[0178] On the other hand, an untreated wafer W is taken out of the cassette Cw by means of the retractable arm 41 or the retractable arm 42 of the transport robot TR (see FIGS. 3 (a) to 3 (c) ). The wafer W is loaded onto the wafer transfer pins 84 through a space between the support posts 79 by the transport robot TR with the center of the wafer W coinciding with the center axis of the rotary pipe 77.

[0179] Then, the system controller 155 controls the susceptor movement mechanism 46 to move the wafer back side press plate 81 a apart from the rotary pipe 77. Thus, the wafer back side press plate 81 a presses the peripheral edge portion of the lower (back) surface of the wafer W, and the peripheral edge portion of the upper surface of the wafer W is pressed against the abutment portion 80 a of the cathode ring 80. That is, the wafer W is held between the wafer back side press plate 81 a and the abutment portion 80 a of the cathode ring 80. Thus, the peripheral edge portion of the upper surface of the wafer W is sealed by the sealing surface 80 s of the abutment portion 80 a, while the cathode 83 is biased toward the wafer W into contact with the peripheral edge portion of the upper surface of the wafer W.

[0180] The system controller 155 controls the inversion driving section 43 to invert the wafer holding/rotating mechanism 74 a so that the wafer W faces downward. Then, the pump P1 is actuated under the control of the system controller 155 to supply the plating liquid into the plating vessel 61 a at a flow rate of 10 1/min (see FIG. 5). Thus, the plating liquid is slightly raised from the edge of the plating vessel 61 a to overflow into the recovery vessel 62 a.

[0181] In turn, the system controller 155 controls the lift mechanism 44 to lower the wafer holding/rotating mechanism 74 a. The lowering rate of the wafer holding/rotating mechanism 74 a is reduced when a distance between the lower surface of the wafer W and the surface of the plating liquid is reduced to not greater than several millimeters. Then, the lower surface of the wafer W is gradually brought into contact with the surface of the plating liquid filled in the plating vessel 61 a. A period from the start of the contact of the wafer W with the plating liquid to the completion of the contact should be such that the seed layer formed on the lower surface of the wafer W is hardly dissolved in the plating liquid. When the distance between the lower surface of the wafer W and the surface of the plating liquid is reduced to several millimeters, the system controller 155 controls the plating power source 82 to apply a first voltage between the anode 76 and the cathode 83.

[0182] With the lower surface of the wafer W in contact with the surface of the plating liquid, the wafer W is spaced about 0.3 mm to about 1 mm from the upper edge of the plating vessel 61 a.

[0183] Subsequently, the system controller 155 controls the rotative driving mechanism 45 to rotate the wafer W at a relatively low rotation speed (e.g., 10 rpm to 100 rpm), and then controls the plating power source 82 to apply a second voltage (plating voltage) between the anode 76 and the cathode 83 for electrical energization for several minutes. Thus, electrons are donated to copper ions in the plating liquid in an interface between the plating liquid and the lower surface of the wafer W connected to the cathode 83, so that copper atoms are deposited on the lower surface of the wafer W. That is, the lower surface of the wafer W is plated with copper.

[0184] Iron ions as an oxidizing/reducing agent are present in the form of divalent or trivalent iron ions in the plating liquid. In this embodiment, the mesh anode 76 has a sufficiently great surface area (e.g., a surface area two to ten times the area to be plated) . Further, the plating liquid can be applied to the entire anode 76 at a sufficiently high flow rate by the shower head 75. Therefore, a sufficient amount of divalent iron ions can be supplied to the anode 76 to promote a reaction in which the divalent iron ions donate electrons to the anode 76 thereby to be turned into trivalent iron ions.

[0185] Thus, the iron ions cyclically experience the oxidization and the reduction, so that the amount of electrons transferred between the plating liquid and the anode 76 is virtually balanced with the amount of electrons transferred between the cathode 83 and the plating liquid.

[0186] Therefore, the plating process is free from bubbles of active oxygen, which may otherwise be generated when the oxidizing/reducing agent is not used. Thus, oxidative decomposition of the additives contained in the plating liquid can be retarded. Further, it is possible to eliminate the possibility that the oxygen bubbles adhere on the lower surface of the wafer W and fill the fine holes or grooves formed in the surface (lower surface) of the wafer W to hinder the plating.

[0187] The plating liquid is drawn by the rotating wafer W in the vicinity of the interface between the plating liquid and the wafer W, and subjected to a centrifugal force. However, the plating liquid can assuredly be introduced into the recovery vessel 62 a to 62 d by the projection 80 p of the cathode ring 80.

[0188] Upon the electrical energization of the plating power source 82, the valve 201V is opened under the control of the system controller 155. Thus, the cathode cleaning liquid is introduced into the fluid channel 81 c. The cathode cleaning liquid flows out of the peripheral openings of the wafer back side press plate 81 a, and is introduced into the cathode cleaning liquid collection vessel 210 through the fluid channels 80 f (see FIG. 8). Thus, the cathode 83, which is disposed in the fluid channels 80 f, is cleaned with the cathode cleaning liquid.

[0189] The plating liquid is present opposite from the cathode 83 with respect to the wafer W and the abutment portion 80 a. Therefore, where the wafer W is properly sealed by the sealing surface 80 s of the abutment portion 80 a, the plating liquid does not flow to the cathode 83. On the other hand, if the sealing between the wafer W and the abutment portion 80 a is insufficient, the plating liquid flows into a gap between the wafer W and the abutment portion 80 a to reach the cathode 83. If the electrically energized cathode 83 is kept in contact with the plating liquid, the cathode 83 is liable to be damaged (plated).

[0190] The plating liquid reaching the cathode 83 is washed away by the cathode cleaning liquid, and flows into the liquid trap 211 from the cathode cleaning liquid collection vessel 210. Since the cathode cleaning liquid and the mixture of the cathode cleaning liquid and the plating liquid differ in electrical conductivity, the system controller 155 can detect the plating liquid reaching the cathode 83 on the basis of the output signal of the conductivity meter 212.

[0191] Then, the system controller 155 controls the plating supply source 82 to stop the electrical energization between the anode 76 and the cathode 83, and controls the lift mechanism 44 to lift the wafer W so that the lower surface of the wafer W is spaced several millimeters apart from the surface of the plating liquid filled in the plating vessel 61 a.

[0192] Further, the system controller 155 controls the rotative driving mechanism 45 to rotate the wafer W at a relatively high speed (e.g., 200 rpm to 1000 rpm) for several tens seconds. Thus, the plating liquid is laterally spun off from the lower surface of the wafer W. At this time, the plated surface of the wafer W is kept covered with a film of the plating liquid rather than completely dried. Thus, the plated surface of the wafer W is prevented from being corroded during transportation of the wafer W.

[0193] Under the control of the system controller 155, the valve 201V is closed and the valve 202V is opened. Thus, the cathode cleaning liquid remaining in the fluid channel 81 c is purged by nitrogen gas, and the cathode cleaning liquid in the fluid channels 80 f is laterally drained by a centrifugal force. The cathode cleaning liquid remaining in the leak pipe 204 may be sucked to be drained by an ejector not shown.

[0194] In turn, the system controller 155 controls the rotative driving mechanism 45 to stop the rotation of the wafer W, and controls the lift mechanism 44 to lift the wafer holding/rotating mechanism 74 a to a predetermined position. Then, the system controller 155 controls the inversion driving section 43 to invert the wafer holding/rotating mechanism 74 a so that the wafer W faces upward.

[0195] Thereafter, the system controller 155 controls the susceptor movement mechanism 46 to move the wafer back side press plate 81 a toward the rotary pipe 77, whereby the wafer W is disengaged from the wafer back side press plate 81 a. At this time, the wafer W is smoothly released from the sealing surface 80 s by the resilience of the cathode 83, so that the wafer W is supported on the wafer transfer pins 84 as shown in FIG. 9. Since the cathode cleaning liquid is not present in the fluid channels 80 f, the cathode leaning liquid does not drip on the upper surface (plated surface) of the wafer W.

[0196] After the wafer W is moved apart from the abutment portion 80 a, the plating liquid remaining on the plated surface of the wafer W is sucked through a gap between the sealing surface 80 s and the wafer W, so that the sealing surface 80 s and the contact portions 83 c of the cathode 83 are contaminated with the plating liquid. However, the plating liquid adhering to the contact portions 83 c is rinsed off with the cathode cleaning liquid when the plating process is performed on the next wafer W (or the dummy wafer D). On the other hand, the plating liquid adhering to the sealing surface 80 s cannot be rinsed off with the cathode cleaning liquid, but remains on the sealing surface 80 s. However, this presents no particular problem, as long as the plating process is sequentially performed with the sealing surface 80 s kept wetted with the plating liquid.

[0197] The treated wafer W is unloaded through the space between the support posts 79 by the retractable arm 42 or the retractable arm 41 of the transport robot TR. Thus, the plating process on the single wafer W is completed.

[0198] The plating process maybe performed simultaneously in the plating cups 56 a to 56 d by simultaneously actuating the four pumps P1 to P4, or in some of the plating cups 56 a to 56 d by actuating corresponding ones of the pumps P1 to P4.

[0199]FIG. 10 is a schematic sectional view illustrating the common construction of the bevel etching units 21 a, 21 b.

[0200] A spin chuck 86 for generally horizontally holding and rotating the wafer W is provided in a generally cylindrical cup 85. The spin chuck 86 is adapted to hold the wafer W by sucking a center portion of the lower surface of the wafer W without contacting the peripheral edge of the wafer W. The spin chuck 86 has a vertical rotation shaft 87, and a rotative driving force is transmitted from a rotative driving mechanism 88 to the rotation shaft 87. A lift mechanism 89 for moving up and down the spin chuck 86 is coupled to the spin chuck 86, so that the spin chuck 86 can be brought into a state where its upper portion is accommodated in the cup 85 and into a state where its upper portion is located above an upper edge of the cup 85.

[0201] The cup 85 includes three cups 85 a to 85 c coaxially arranged. The outermost one 85 a of the cups 85 a to 85 c has an upper edge located at the highest position, and the middle cup 85 b has an upper edge located at the lowest position. An annular treatment liquid guide plate 85 d as seen in plan is coupled to an upper edge of the innermost cup 85 c. An outer edge of the treatment liquid guide plate 85 d is bent to be inserted into a space between the cup 85 a and the cup 85 b.

[0202] A treatment liquid collection vessel 97 having an open top is defined between the cup 85 a and the cup 85 b, and an air outlet vessel 98 is defined between the cup 85 b and the cup 85 c. A liquid drain port 97 a is provided in the bottom of the treatment liquid collection vessel 97, and an air outlet port 98 a is provided in the bottom of the air outlet vessel 98.

[0203] A rinse nozzle 90A and an etching nozzle 90B are provided above the cup 85. A rinse liquid pipe 91 is connected in communication with the rinse nozzle 90A, and a rinse liquid supply source 92 is connected to the rinse liquid pipe 91. A valve 91V is provided in the rinse liquid pipe 91. By opening the valve 91V, the rinse liquid can be discharged through the rinse nozzle 90A to be supplied to the upper surface of the wafer W held by the spin chuck 86. The rinse liquid may, for example, deionized water.

[0204] The etching nozzle 90B is connected via the post-treatment agent pipe P14 to an etching liquid supply source 96 disposed in the post-treatment agent supply section 4 (see FIG. 1) and containing the etching liquid. A valve 90BV is provided in the post-treatment agent pipe P14 between the etching liquid supply source 96 and the etching nozzle 90B. By opening the valve 90BV, the etching liquid can be supplied onto the upper surface of the wafer W held by the spin chuck 86 through the etching nozzle 90B. The flow rate of the etching liquid can also be adjusted by the valve 90BV. The etching liquid may be, for example, a mixture of sulfuric acid, a hydrogen peroxide and water.

[0205] Another rinse nozzle 99 extends through the treatment liquid guide plate 85 d from the lower side. A rinse liquid pipe 100 is connected in communication with the rinse nozzle 99, and the rinse liquid supply source 92 is connected to the rinse liquid pipe 100. A valve 100V is provided in the rinse liquid pipe 100. By opening the valve 100V, the rinse liquid can be discharged through the rinse nozzle 99 to be supplied to the lower surface of the wafer W held by the spin chuck 86.

[0206] An etching pipe 93 is provided generally vertically above the cup 85. The etching pipe 93 has a groove 94 provided in a lower end portion thereof as opening horizontally toward the center of the cup 85 in association with the surface of the wafer W held by the spin chuck 86. The peripheral edge of the wafer W can be inserted in the groove 94. The inner space of the groove 94 and the inner space of the etching pipe 93 communicate with each other.

[0207] A movement mechanism 95 is coupled to the etching pipe 93. The etching pipe 93 can be moved vertically and radially of the cup 85 by the movement mechanism 95. Thus, the etching pipe 93 can be moved between a treatment position at which the peripheral edge of the wafer W is inserted in the groove 94 and a retracted position at which the etching pipe 93 is retracted from the treatment position apart from the wafer W. The etching pipe 93 can also be retracted laterally beyond the cup 85.

[0208] The etching pipe 93 is connected via the post-treatment agent pipe P14 to the etching liquid supply source 96 disposed in the post-treatment agent supplying section 4 (see FIG. 1) and containing the etching liquid. A valve 93V is provided in the post-treatment agent pipe P14 between the etching pipe 93 and the etching liquid supply source 96. By opening the valve 93V, the etching liquid can be supplied to the inner space of the groove 94. The flow rate of the etching liquid can also be adjusted by the valve 93V.

[0209] The operations of the rotative driving mechanism 88, the lift mechanism 89 and the movement mechanism 95, and the opening and closing of the valves 90BV, 91V, l00V, 93V are controlled by the system controller 155.

[0210] When the peripheral edge of the wafer W is to be etched by the bevel etching unit 21 a, 21 b, the system controller 155 first controls the movement mechanism 95 to retract the etching pipe 93 at the retracted position.

[0211] In turn, the system controller 155 controls the lift mechanism 89 to move up the spin chuck 86 so that the upper portion of the spin chuck 86 is located above the upper edge of the cup 85. The wafer W subjected to the plating process in the plating section 12 is loaded into the bevel etching unit 21 a or 21 b by the retractable arm 41 or the retractable arm 42 of the transport robot TR (see FIGS. 3(a) to 3(c)), and held by the spin chuck 86 by suction with the center of the wafer W coinciding with the center axis of the rotation shaft 87. The surface of the wafer W subjected to the plating process faces upward.

[0212] Thereafter, the system controller 155 controls the lift mechanism 89 to move down the spin chuck 86. Thus, the wafer W held by the spin chuck 86 is surrounded by the cup 85 a. Then, the system controller 155 controls the rotative driving mechanism 88 to rotate the wafer W held by the spin chuck 86. The rotation speed of the wafer W is, for example, about 500 rpm.

[0213] In this state, the valves 91V and 100V are opened under the control of the system controller 155. Thus, the rinse liquid is supplied to the upper and lower surfaces of the wafer W from the rinse nozzles 90A and 99. The rinse liquid spreads toward the peripheral edge of the wafer W by a centrifugal force, and flows over the entire upper surface of the wafer W and the lower surface of the wafer W except a portion thereof in contact with the spin chuck 86. Thus, the wafer W is cleaned.

[0214] The rinse liquid is spun off laterally of the wafer W by the centrifugal force, and flows over the interior of the cup 85 a and the upper surface of the treatment liquid guide plate 85 d down into the treatment liquid collection vessel 97. The rinse liquid is introduced into a collection tank not shown through the liquid drain port 97 a. Further, gas is exhausted from the cup 85 through the air outlet port 98 a by an air exhauster system not shown. Thus, mist of the rinse liquid and the like are prevented from scattering out of the cup 85.

[0215] After the rinsing process is performed for a predetermined period, the valves 91V, 100V are closed under the control of the system controller 155. The wafer W is continuously rotated, whereby the rinse liquid remaining on the wafer W is mostly spun off.

[0216] Subsequently, the system controller 155 controls the movement mechanism 95 to move the etching pipe 93 to the treatment position. Thus, the peripheral edge of the wafer W is inserted in the groove 94 as shown in FIG. 10. At this time, the rotation speed of the wafer W may be, for example, about 500 rpm. Then, the valve 93V is opened under the control of the system controller 155. The flow rate of the etching liquid may be, for example, 20 ml/min. Thus, the etching liquid is supplied into the groove 94 from the etching liquid supply source 96. The etching liquid flows out of the groove 94, so that the groove 94 is virtually filled with the etching liquid.

[0217] Since the peripheral edge of the wafer W is inserted in the groove 94, a part of the thin copper film formed on the peripheral edge of the wafer W is dissolved by the etching liquid. With the wafer W being rotated, the peripheral edge of the wafer W is moved relative to the etching pipe 93 located at the treatment position. As a result, the entire peripheral edge of the wafer W is etched. An etching width is determined by an insertion depth of the wafer W in the groove 94, so that the etching process can accurately be performed with a desired etching width.

[0218] Like the rinse liquid, the etching liquid spun off laterally of the wafer W by a centrifugal force is once collected in the collection vessel 97, and then introduced into the collection tank not shown through the liquid drain port 97 a. During this period, gas is continuously exhausted through the air outlet port 98 a, so that mist of the etching liquid is prevented from scattering out of the cup 85.

[0219] After the etching liquid is continuously supplied for a predetermined period (e.g., several tens seconds) for the etching of the thin copper film on the peripheral edge of the wafer W, the valve 93V is closed under the control of the system controller 155 to stop the supply of the etching liquid to the groove 94. Thus, the etching process for etching the peripheral edge of the wafer W is completed in the absence of the etching liquid in the groove 94.

[0220] Thereafter, the valves 91V, 100V are opened again under the control of the system controller 155 to supply the rinse liquid to the surfaces of the wafer W. Thus, the etching liquid remaining on the peripheral edge portion of the wafer W is rinsed away with the rinse liquid. During this period, the system controller 155 controls the movement mechanism 95 to move the etching pipe 93 to the retracted position.

[0221] After the rinse liquid is continuously supplied for a predetermined period (e.g., about one minute), the valves 91V, 100V are closed under the control of the system controller 155 to stop the supply of the rinse liquid. The system controller 155 controls the rotative driving mechanism 88 to rotate the spin chuck 86 at a high rotation speed (e.g., about 1000 rpm) for a predetermined period (e.g., several tens seconds) for spinning off the rinse liquid from the wafer W for drying. Then, the rotation of the spin chuck 86 is stopped.

[0222] Subsequently, the system controller 155 controls the lift mechanism 89 to move up the spin chuck 86 so that the wafer W held by the spin chuck 86 is located above the upper edge of the cup 85. Then, the wafer W is released out of the suction-held state.

[0223] In turn, the treated wafer W is unloaded by the retractable arm 42 or the retractable arm 41 of the transport robot TR. Thus, the etching process for the etching of the peripheral edge of the single wafer W is completed. Since no thin copper film is present on the peripheral edge of the treated wafer W, there is no possibility that copper adheres on the substrate holder hand 41 c, 42 c when the peripheral edge of the wafer W is held by the substrate holder hand 41 c, 42 c (see FIG. 3(a)) in the subsequent steps.

[0224] In this embodiment, the cup 85 is fixed, and the spin chuck 86 is adapted to be moved up and down by the lift mechanism 89. However, it is merely necessary to vertically move the spin chuck 86 and the cup 85 relative to each other. For example, the spin chuck 86 may vertically be fixed, and the cup 85 may be adapted to be moved up and down. Even in this case, the upper portion of the spin chuck 86 can be located above the upper edge of the cup 85, so that the wafer W can be loaded and unloaded by the retractable arm 41 or the retractable arm 42.

[0225] The dummy wafer D having one surface plated with copper in the plating unit 20 a to 20 d is subjected to an etching process in the bevel etching unit 21 a, 21 b for removal of the copper film formed by the plating, so that the dummy wafer D can be reuse for the plating. For the removal of the copper film on the dummy wafer D, the dummy wafer D is held by the spin chuck 86 so that the surface of the dummy wafer D plated in the plating section 12 faces upward as in the case of the bevel etching of the wafer W. The etching process for removing the entire copper film formed on the dummy wafer D is performed in substantially the same manner as in the aforesaid bevel etching process, except that the etching liquid is not ejected from the etching pipe 93 but from the etching nozzle 90B.

[0226] More specifically, the valve 90BV is opened for a predetermined period under the control of the system controller 155 to supply the etching liquid over the upper surface of the dummy wafer D. At this time, the system controller 155 controls the rotative driving mechanism 88 to stop the rotation of the spin chuck 86 or rotate the spin chuck 86 at a low speed. Thus, no centrifugal force or a reduced centrifugal force is exerted on the etching liquid on the dummy wafer D. Therefore, a greater amount of the etching liquid remains in a raised state on the dummy wafer D as compared with the case where the spin chuck 86 is rotated at a high speed. Thus, the copper film can efficiently be etched by the etching liquid, so that the etching liquid is saved.

[0227] For the supply of the etching liquid, the etching liquid may continuously be supplied by keeping the valve 90BV open. Alternatively, the etching of the copper film on the dummy wafer D may be achieved by repeating such a process that the etching liquid is supplied to be raised on the entire surface of the dummy wafer D standing still or rotated at a low speed, then the valve 90BV is closed to stop the supply of the etching liquid and, after a lapse of a predetermined period, the spin chuck 86 is rotated at a high speed to spin off the etching liquid.

[0228] By thus performing the etching process, the copper film formed on the dummy wafer D can completely be removed (or stripped). Since the units for removing the copper film formed on the dummy wafer D are provided separately from the plating units 20 a to 20 d, the plating process can properly be performed in the plating units 20 a to 20 d without any influence of the etching process. Further, it is possible to completely remove the copper film from the dummy wafer D, because the conditions for the removal of the copper film formed on the dummy wafer D are not constrained by the plating units 20 a to 20 d.

[0229] After the removal of the copper film by the etching liquid, the dummy wafer D is rinsed with the rinse liquid, and the rinse liquid is spun off for drying as in the bevel etching process.

[0230]FIG. 11 is a schematic sectional view illustrating the common construction of the cleaning units 22 a, 22 b.

[0231] A spin chuck 102 for generally horizontally holding and rotating the wafer W is provided in a generally cylindrical cup 101. The spin chuck 102 includes a vertical rotation shaft 102 a and a disk spin base 102 b provided at an upper end of the rotation shaft 102 a perpendicularly to the rotation shaft 102 a. A plurality of chuck pins 102 e are provided upright on a peripheral edge portion of an upper surface of the spin base 102 b in circumferentially spaced relation. The chuck pins 102 e cooperatively support a peripheral edge portion of the lower surface of the wafer W in abutment against the peripheral surface (circumferential surface) of the wafer W for holding the wafer W.

[0232] A rotative driving force is transmitted to the rotation shaft 102 a of the spin chuck 102 from a rotative driving mechanism 103. A lift mechanism 104 for moving up and down the spin chuck 102 is coupled to the spin chuck 102, so that the spin chuck 102 can be brought into a state where its upper portion is accommodated in the cup 101 and into a state where its upper portion is located above an upper edge of the cup 101.

[0233] The cup 101 includes three cups 101 a to 101 c coaxially arranged. The outermost one 101 a of the cups 101 a to 101 c has an upper edge located at the highest position, and the middle cup 101 b has an upper edge located at the lowest position. An annular treatment liquid guide plate 101 d as seen in plan is coupled to an upper edge of the innermost cup 101 c. An outer edge of the treatment liquid guide plate 101 d is bent to be inserted into a space between the cup 101 a and the cup 101 b.

[0234] A treatment liquid collection vessel 105 having an open top is defined between the cup 101 a and the cup 101 b, and an air outlet vessel 106 is defined between the cup 101 b and the cup 101 c. A liquid drain port 105 a is provided in the bottom of the treatment liquid collection vessel 105, and an air outlet port 106 a is provided in the bottom of the air outlet vessel 106.

[0235] A nozzle 107 is provided above the cup 101. The nozzle 107 is connected in communication with the rinse liquid supply source via a valve 107V. By opening the valve 107V, the rinse liquid can be discharged toward the wafer W held by the spin chuck 102 from the nozzle 107.

[0236] The rotation shaft 102 a has a treatment liquid supply channel 102 c extending axially therethrough, and an open upper end serving as a treatment liquid outlet port 102 d. The cleaning liquid can be supplied into the treatment liquid supply channel 102 c through the post-treatment agent pipe P14 from a cleaning liquid supply source provided in the post-treatment agent supplying section 4 (see FIG. 1) The rinse liquid can also be supplied into the treatment liquid supply channel 102 c from the rinse liquid supply source. The cleaning liquid maybe, for example, a mixture of sulfuric acid, a hydrogen peroxide and water.

[0237] A valve 108V is provided between the treatment liquid supply channel 102 c and the cleaning liquid supply source. A valve 109V is provided between the treatment liquid supply channel 102 c and the rinse liquid supply source. By closing the valve 109V and opening the valve 108V, the cleaning liquid can be discharged from the treatment liquid outlet port 102 d. By closing the valve 108V and opening the valve 109V, the rinse liquid can be discharged from the treatment liquid outlet port 102 d. Thus, the cleaning liquid or the rinse liquid can be supplied to the center of the lower surface of the wafer W held by the spin chuck 102.

[0238] The operations of the rotative driving mechanism 103 and the lift mechanism 104, and the opening and closing of the valves 107V, 108V, 109V are controlled by the system controller 155.

[0239] When the wafer W is to be cleaned in the cleaning unit 22 a or 22 b, the system controller 155 first controls the lift mechanism 104 to move up the spin chuck 102 so that the upper portion of the spin chuck 102 is located above the upper edge of the cup 101. The wafer W subjected to the bevel etching process in the bevel etching unit 21 a or 21 b is loaded into the cleaning unit 22 a or 22 b by the retractable arm 41 or the retractable arm 42 of the transport robot TR (see FIGS. 3(a) to 3(c)), and mechanically held by the chuck pins 102 e with the center of the wafer W coinciding with the center axis of the rotation shaft 102 a.

[0240] Thereafter, the system controller 155 controls the lift mechanism 104 to move down the spin chuck 102. Thus, the wafer W held by the spin chuck 102 is surrounded by the cup 101 a. Then, the system controller 155 controls the rotative driving mechanism 103 to rotate the wafer W held by the spin chuck 102. The rotation speed of the wafer W is, for example, about 500 rpm. Gas is exhausted from the cup 101 through the air outlet port 106 a by the exhauster system not shown.

[0241] In this state, the valves 107V, 108V are opened under the control of the system controller 155. Thus, the rinse liquid and the cleaning liquid are discharged toward the wafer W from the nozzle 107 and the treatment liquid outlet port 102 d, respectively. The rinse liquid and the cleaning liquid supplied to the surfaces of the wafer W spread toward the peripheral edge of the wafer W by a centrifugal force. Thus, the entire lower surface of the wafer W is cleaned.

[0242] The rinse liquid and the cleaning liquid are spun off laterally of the wafer W by the centrifugal force, and flows over the interior of the cup 101 a and the upper surface of the treatment liquid guide plate 101 d down into the treatment liquid collection vessel 105. The rinse liquid and the cleaning liquid are introduced into the collection tank not shown through the liquid drain port 105 a. Further, gas is exhausted from the cup 101. Thus, mist of the cleaning liquid can be exhausted through the air outlet port 106 a so as to be prevented from scattering out of the cup 101.

[0243] After this process is performed for a predetermined period, the valve 108V is closed and the valve 109V is opened under the control of the system controller 155. Thus, the rinse liquid is discharged toward the lower surface of the wafer W from the treatment liquid outlet port 102 d. The supply of the rinse liquid to the upper surface of the wafer W from the nozzle 107 is continued. Thus, the cleaning liquid is rinsed away from the lower surface of the wafer W. After this process is continued for a predetermined period (e.g., about one minute), the valves 107V and 109V are closed under the control of the system controller 155 to stop the supply of the rinse liquid to the wafer W.

[0244] Subsequently, the system controller 155 controls the rotative driving mechanism 103 to rotate the wafer W held by the spin chuck 102 at a high speed, for example, at about 2000 rpm. Thus, the rinse liquid remaining on the wafer W is mostly spun off for drying the wafer W. After the high-speed rotation of the wafer W is continued for a predetermined period (e.g., several tens seconds), the system controller 155 controls the rotative driving mechanism 103 to stop the rotation of the wafer W.

[0245] In turn, the system controller 155 controls the lift mechanism 104 to move up the spin chuck 102 so that the wafer W held by the spin chuck 102 is located above the upper edge of the cup 101. Thus, the wafer W is released from the chuck pins 102 e.

[0246] Then, the treated wafer W is unloaded by the retractable arm 42 or the retractable arm 41 of the transport robot TR. Thus, the cleaning process for the cleaning of the single wafer W is completed.

[0247] In this embodiment, the cup 101 is fixed, and the spin chuck 102 is adapted to be moved up and down by the lift mechanism 104. However, it is merely necessary to vertically move the spin chuck 102 and the cup 101 relative to each other. For example, the spin chuck 102 may vertically be fixed, and the cup 101 may be adapted to be moved up and down. Even in this case, the spin base 102 b can be located above the upper edge of the cup 101, so that the wafer W can be loaded and unloaded by the retractable arm 41 or the retractable arm 42.

[0248]FIG. 12 is a block diagram illustrating the construction of a control system for the wafer treating section 1.

[0249] The system controller 155 controls the wafer treating section 1, the major constituent managing section 2, the minor constituent managing section 3 and the post-treatment agent supplying section 4 to comprehensively manage the entire plating apparatus 10. More specifically, the system controller 155 monitors the states of the respective sections, issues proper control commands to the respective sections, generates data for the respective sections, and takes in data from the respective sections.

[0250] Hardware of the system controller 155 includes a central processing unit (CPU) having a processing capability of 10 MIPS (million instructions per second) or more, a semiconductor memory having a storage capacity of 10 Mbytes or more, a magnetic memory having a storage capacity of 1 Mbyte or more, RS-232C compatible serial ports, RS-485 compatible serial ports, and a plurality of printed circuit boards. The magnetic memory may be, for example, a hard disk (HD) incorporated in a hard disk drive (HDD), or a flexible disk (FD) to be inserted in a flexible disk drive (FDD).

[0251] Software employed in the system controller 155 includes an operating system, and application programs which are at least partly described in a high-level language. These programs are stored in a storage device 155M provided in the system controller 155. The application programs include recipes for performing the plating process, the bevel etching process, the cleaning process, the process employing the dummy wafer D, and the like.

[0252] The system controller 155 is connected to a display 156, a keyboard 157, a pointing device (e.g., a mouse) 156 p, so that the operator can interact with the system controller 155 for inputting and outputting information. The system controller 155 is further connected to an audible alarm generator 158. When a certain event occurs, e.g., when the residual amount of the copper supply source (copper tube) for supplying copper ions to the plating liquid is reduced below a predetermined level, an audible alarm is given, and information on the alarm is displayed on the display 156.

[0253] The system controller 155 is connected to the transport controller 29 (see FIG. 2), the major constituent managing section 2 and the minor constituent managing section 3 via the RS-232C compatible serial ports by cables. The system controller 155 is further connected to a motor controller 159 by a pulse-string input/output cable, and connected to a pump controller 160, the flow meters 60 a to 60 d and the absorptiometers 66A and 66B by analog signal cables.

[0254] Thus, the system controller 155 is capable of controlling motors provided in the rotative driving mechanisms 45, 88, 103 (see FIGS. 7, 10 and 11), for example, via the motor controller 159, and controlling the operations of the pumps P1 to P4 (see FIG. 5) in the plating section 12, for example, via the pump controller 160. Signals indicative of the flow rates from the flow meters 60 a to 60 d (see FIG. 5) are inputted as analog signals to the system controller 155. Further, the system controller 155 controls the operations of the absorptiometers 66A, 66B (e.g., light emission of the light emitting sections 68A, 68B) on an analog signal basis, and receives analog signals outputted from the light receiving sections 69A, 69B.

[0255] The system controller 155 is further connected to the major constituent managing section 2, the post-treatment agent supplying section 4 and serial/parallel converters 161 a, 161 b via the RS-485 compatible serial ports by cables. In FIG. 12, only two serial/parallel converters 161 a, 161 b are shown, but the system controller 155 may be connected to a greater number of serial/parallel converters.

[0256] The serial/parallel converters 161 a and 161 b are respectively connected to electromagnetic valves 162 a and 62 b, and sensors 163 a and 163 b (e.g., the temperature sensor 70, the electromagnetic conductivity meter 71, the ultrasonic level meter 72 (see FIG. 5)) via parallel cables. The electromagnetic valves 162 a, 162 b are capable of controlling air valves (e.g., the valves 91V, 100V (see FIG. 10) and the valve 107V (see FIG. 11)).

[0257] Information on a production plan can be inputted to the storage device 155M of the system controller 155 via the keyboard 157 or the pointing device 156 p as an inputting device. More specifically, the number of wafers W intended to be plated (in each production lot) can be inputted. Further, the system controller 155 counts the number of actually treated wafers W out of the intended wafers W on the basis of a control history of the transport robot TR.

[0258] Therefore, the system controller 155 can detect the discontinuation of the loading of the wafer W in the plating units 20 a to 20 d by comparing the number of the wafers W loaded to be plated with the number of the treated wafers W. Where the production plan includes a plurality of production lots, information indicative of whether or not these lots are to be sequentially dealt with can be inputted to the system controller 155. Thus, the system controller 155 can predict whether or not the loading of the wafer W in the plating units 20 a to 20 d is discontinued after each of the lots.

[0259]FIG. 13 is a schematic diagram illustrating the construction of the major constituent managing section 2.

[0260] The major constituent managing section 2 includes at least one copper dissolution tank (two copper dissolution tanks 110 a, 110 b in this embodiment) containing copper tubes 146 (copper supply source) for supplying copper ions to the plating liquid, a buffer container 111 for supplying a replacement liquid to one of the copper dissolution tanks 110 a, 110 b not in use, and an undiluted replacement liquid supplying section 112 for supplying an undiluted replacement liquid as a source of the replacement liquid to the buffer container 111.

[0261] The copper dissolution tanks 110 a, 110 b each have a cylindrical sealed structure having a closed bottom and a generally vertical axis. The copper dissolution tank 110 a, 110 b is placed on a weight meter 154 a, 154 b, which is adapted to measure the total weight of the copper dissolution tank 110 a, 110 b including its content.

[0262] The copper dissolution tank 110 a, 110 b includes an outer pipe 116 a, 116 b constituting a side wall thereof, and an inner pipe 117 a, 117 b provided in the outer pipe 116 a, 116 b. An inner space of the inner pipe 117 a, 117 b communicates with a space (hereinafter referred to as “annular space 145”) defined between the outer pipe 116 a, 116 b and the inner pipe 117 a, 117 b in a lower portion of the copper dissolution tank 110 a, 110 b. Copper tubes are placed in the annular space 145.

[0263] The buffer container Ill has a cover 120 having piping ports for piping, and is virtually sealed. Upper and lower portions of the buffer container 111 are connected in communication with each other by a bypass pipe 125 vertically extending along the exterior of the buffer container 111. A constant volume check sensor 126 is provided at a predetermined height on a lateral side of the bypass pipe 125 for detecting the presence or absence of liquid at this predetermined height within the bypass pipe 125.

[0264] The liquid (e.g., the replacement liquid) is allowed to freely flow between the buffer container 111 and the bypass pipe 125, so that a liquid surface level in the buffer container 111 is virtually equal to a liquid surface level in the bypass pipe 125. Thus, the presence or absence of the liquid at the predetermined height in the buffer container 111 can be detected by the constant volume check sensor 126.

[0265] One end of a circulation pipe 118 is connected to the bottom of the buffer container 111 via a piping port for communication between the circulation pipe 118 and the buffer container 111. The other end of the circulation pipe 118 is branched into branch circulation pipes 121, 122 at a branch point Bi. The branch circulation pipe 121 is further branched into branch circulation pipes 121 a, 121 b, while the branch circulation pipe 122 is further branched into branch circulation pipes 122 a, 122 b.

[0266] The branch circulation pipes 121 a and 121 b are respectively connected to upper portions of the inner pipes 117 a and 117 b of the copper dissolution tanks 110 a and 110 b. The branch circulation pipes 122 a and 122 b are respectively connected to liquid outlet pipes 149 a and 149 b provided in the copper dissolution tanks 110 a and 110 b. Valves AV3-2 and AV4-2 are provided in the branch circulation pipes 121 a and 121 b, respectively. Valves AV3-3 and AV4-3 are provided in the branch circulation pipes 122 a and 122 b, respectively.

[0267] Branch circulation pipes 119 a and 119 b are respectively connected in communication with the annular spaces 145. Valves AV3-1 and AV4-1 are provided in the branch circulation pipes 119 a and 119 b, respectively. The branch circulation pipes 119 a, 119 b are connected to one end of a circulation pipe 119. The other end of the circulation pipe 119 is branched into branch circulation pipes 119 d and 119 e at a branch point B2.

[0268] The valves AV3-1, AV3-2, AV3-3, AV4-1, AV4-2, AV4-3 are collectively disposed in a copper dissolution tank channel switching section 153.

[0269] The branch circulation pipe 119 d extends into the buffer container 111 through the cover 120 (through the piping port formed in the cover 120). A valve AV2-2 is provided in the branch circulation pipe 119 d .

[0270] One end of a channel switching pipe 115 is connected to the circulation pipe 118 at a branch point B3. Liquid can be drained from the other end of the channel switching pipe 115. A valve AV1-4 is provided at the other end of the channel switching pipe 115. The plating liquid transport pipes P12 a and P12 b are connected to the channel switching pipe 115 via valves AV1-3 and AV1-2, respectively.

[0271] A valve AV1-1 is provided in the circulation pipe 118 between the buffer container 111 and the branch point B3. A valve AV1-5, a pump P5 and a flow meter 123 are provided in the circulation pipe 118 between the branch point B3 and the branch point B1 in this order from the branch point B3. An emptiness check sensor 127 is provided on a lateral side of the circulation pipe 118 in the vicinity of the buffer container 111 (between the buffer container 111 and the branch point B3) . The emptiness check sensor 127 is capable of detecting the presence or absence of the liquid at the height of the emptiness check sensor 127 in the circulation pipe 118. This makes it possible to determine whether or not the buffer container 111 is empty.

[0272] The valves AV1-1, AV1-2, AV1-3, AV1-4, AV1-5 are collectively disposed in an inlet-side main channel switching section 113.

[0273] The branch circulation pipe 119 e is connected to the plating liquid transport pipe P12 b at a branch point B4. A valve AV2-1 is provided in the branch circulation pipe 119 e. The valves AV2-1, AV2-2 are collectively disposed in an outlet-side main channel switching section 114.

[0274] The undiluted replacement liquid supplying section 112 includes an undiluted replacement liquid tank 128 containing the undiluted replacement liquid, and a measure cup 129 for dispensing a predetermined amount of the undiluted replacement liquid. The undiluted replacement liquid may be, for example, concentrated sulfuric acid. The measure cup 129 has a cover 129 a, and is virtually sealed. The measure cup 129 has a bottom having an inverted cone shape. An undiluted replacement liquid transport pipe 130 extends from an upper portion of the measure cup 129 into a bottom portion of the undiluted replacement liquid tank 128. A valve AV6-3 is provided in the undiluted replacement liquid transport pipe 130.

[0275] The undiluted replacement liquid supplying section 112 is connected to the buffer container 111 by an undiluted replacement liquid supply pipe 124. The undiluted replacement liquid supply pipe 124 extends to the upper portion of the measure cup 129 through the cover 129 a. One end of an undiluted replacement liquid transport pipe 131 is connected to the bottom of the measure cup 129. The other end of the undiluted replacement liquid transport pipe 131 is connected to the undiluted replacement liquid supply pipe 124 at a branch point B5. A valve AV6-1 is provided in the undiluted replacement liquid supply pipe 124 between the branch point B5 and the measure cup 129. A valve AV6-2 is provided in the undiluted replacement liquid transport pipe 131.

[0276] A leak pipe 132 extends through the cover 129 a to be connected in communication with the measure cup 129. A valve AV6-4 is provided in the leak pipe 132 outside the measure cup 129. By opening the valve AV6-4, the internal pressure of the measure cup is set at the atmospheric pressure.

[0277] A constant volume check sensor 133 is provided at a predetermined height on a lateral side of the measure cup 129 for detecting the presence or absence of liquid at this predetermined height in the measure cup 129. An emptiness check sensor 134 is provided on a lateral side of the undiluted replacement liquid transport pipe 131 in the vicinity of the measure cup 129. The emptiness check sensor 134 is capable of detecting the presence or absence of liquid at the height of the emptiness check sensor 134 in the undiluted replacement liquid transport pipe 131. This makes it possible to determine whether or not the measure cup 129 is empty.

[0278] A deionized water supply pipe 135 extends through the cover 120 to be connected in communication with the buffer container 111. Thus, deionized water can be supplied to the buffer container 111 from a deionized water supply source not shown. A valve AV7-1 is provided in the deionized water supply pipe 135.

[0279] An air inlet/outlet pipe 136 is introduced into the buffer container 111 through the cover 120. An air pump 137 is connected to an end of the air inlet/outlet pipe 136 outside the buffer container 111. A three-way valve AV8-3 is provided in the air inlet/outlet pipe 136. The three-way valve AV8-3 is adapted to selectively establish air communication between the buffer container 111 and the air pump 137 and between the buffer container 111 and the atmosphere.

[0280] The air pump 137 has an air exhaustion pipe 138 and an air supply pipe 139. The air inlet/outlet pipe 136 is connected in communication with the air exhaustion pipe 138 and the air supply pipe 139. A three-way valve AV8-1 is provided in the air exhaustion 138, while a three-way valve AV8-2 is provided in the air supply pipe 139. The three-way valves AV8-1, AV8-2, AV8-3, which may be air valves, are collectively disposed in a pressure increasing/reducing section 164.

[0281] Air can be supplied into the buffer container 111 by establishing communication between the atmosphere and the air pump 137 through the three-way valve AV8-1 and between the air pump 137 and the air inlet/outlet pipe 136 through the three-way valve AV8-2, and actuating the air pump 137. Gas can be exhausted from the buffer container 111 by establishing communication between the air inlet/outlet pipe 136 and the air pump 137 through the three-way valve AV8-1 and between the air pump 137 and the atmosphere through the three-way valve AV8-2, and actuating the air pump 137.

[0282] The opening and closing of the valve AV7-1 and the valves in the inlet-side main channel switching section 113, the outlet-side main channel switching section 114, the copper dissolution tank channel switching section 153, the undiluted replacement liquid supplying section 112 and the pressure increasing/reducing section 164, and the operations of the pump P5 and the air pump 137 are controlled by the system controller 155 of the wafer treating section 1 via the serial/parallel converter 165. Output signals of the constant volume check sensors 126, 133, the emptiness check sensors 127, 134, the flow meter 123 and the weight meters 154 a, 154 b are inputted to the system controller 155 of the wafer treating section 1 via the serial/parallel converter 165.

[0283]FIG. 14 is a block diagram illustrating the construction of control systems for the major constituent managing section 2, the minor constituent managing section 3 and the post-treatment agent supplying section 4.

[0284] The major constituent managing section 2 includes the serial/parallel converter 165 and an operation panel 166. The system controller 155 provided in the wafer treating section 1 is connected to the serial/parallel converter 165 via the RS-485 compatible serial port by a cable, and connected to the operation panel 166 via the RS-232C compatible serial port by a cable.

[0285] Electromagnetic valves 167 and sensors 168 (e.g., the constant volume check sensors 126, 133, the emptiness check sensors 127, 134 and the weight meters 154 a, 154 b (see FIG. 13)) are connected in parallel to the serial/parallel converter 165. The electromagnetic valves 167 are capable of controlling air valves (e.g., the valve AV1-1 and the like (see FIG. 13)). The operator can input and output information on the major constituent managing section 2 by means of the operation panel 166.

[0286] The minor constituent managing section 3 includes a minor constituent management controller 169, so that a control operation can be performed independently of the system controller 155 provided in the wafer treating section 1. The minor constituent management controller 169 is connected to the system controller 155 via the RS-232C compatible serial port by a cable.

[0287] A display 170, a keyboard 171, a potentiostat (power source) 172, a syringe pump 173 and a serial/parallel converter 174 are connected to the minor constituent management controller 169. The display 1.70 and the keyboard 171 permit the operator to interact with the minor constituent management controller 169 for inputting and outputting information.

[0288] The syringe pump 173 is capable of adding an indicator and the like dropwise to a sampled plating liquid when the concentrations of the minor constituents of the plating liquid are measured. Further, the syringe pump 173 is capable of quantitatively dispensing replenishment liquids respectively containing the minor constituents in required amounts.

[0289] Electromagnetic valves 175 and sensors 176 (e.g., surface level sensors) are connected to the serial/parallel converter 174 by parallel cables. The electromagnetic valves 175 are capable of controlling air valves.

[0290] The post-treatment agent supplying section 4 includes a serial/parallel converter 177. The system controller 155 provided in the wafer treating section 1 is connected to the serial/parallel converter 177 via the RS-485 compatible serial port by a cable. Electromagnetic valves 178 and sensors 179 are connected to the serial/parallel converter 177 by parallel cables. The electromagnetic valves 178 are capable of controlling air valves (e.g., the valve 93V (see FIG. 10) and the valve 108V (see FIG. 11)).

[0291] With reference to FIG. 13, an explanation will hereinafter be given to the operation of the major constituent managing section 2 during the plating process performed in the plating section 12.

[0292] Prior to the plating process, the system controller 155 determines which of the copper dissolution tanks 110 a, 110 b is to be used. One of the copper dissolution tanks 110 a, 110 b which contains tubes 146 whose total weight is the lightest is used. The other copper dissolution tank is not used, but reserved as a spare.

[0293] Data of the net weights of the respective copper dissolution tanks 110 a, 110 b and the weights of the respective copper dissolution tanks 110 a, 110 b measured when the plating liquid is filled therein is preliminarily inputted into the memory of the system controller 155. The system controller 155 calculates the weights of copper tubes 146 in the copper dissolution tanks 110 a, 110 b on the basis of the output signals of the weight meters 154 a, 154 b.

[0294] It is herein assumed that the weight of the copper tubes 146 in the copper dissolution tank 110 a is judged to be the lightest and sufficient to supply copper ions to the plating liquid for a predetermined period. In this case, a flow channel is established for circulating the plating liquid through the plating section 12 and the copper dissolution tank 110 a under the control of the system controller 155. More specifically, the valves AV1-3, AV1-5, AV3-2, AV3-1, AV2-1 are opened, and the other valves are closed.

[0295] In this state, the pump P5 is actuated under the control of the system controller 155. Thus, the plating liquid is supplied into the copper dissolution tank 110 a from the plating section 12, flows over the interior and exterior surfaces of the copper tubes 146 in the copper dissolution tank 110 a, and returned into the plating section 12. In the copper dissolution tank 110 a, the copper tube 146 is deprived of electrons by trivalent iron ions in the plating liquid, whereby the trivalent iron ions are reduced to divalent iron ions. Copper ions are leached into the plating liquid from the copper tubes 146 deprived of the electrons.

[0296] Thus, the copper ions are supplied from the copper tubes 146, while being consumed on the lower surface of the wafer W or the dummy wafer D during the plating process. On the other hand, the trivalent iron ions are reduced to the divalent iron ions in the vicinity of the copper tubes 146, while the divalent iron ions are oxidized into trivalent iron ions in the vicinity of the anode 76.

[0297] Where the concentrations of the copper ions, the divalent iron ions and the trivalent iron ions in the plating liquid are not within the predetermined concentration ranges, the plating process cannot properly be performed with a poorer capability of filling the holes or grooves formed in the surface of the wafer W with copper. Therefore, the concentrations of the copper ions and the divalent and trivalent iron ions in the plating liquid should be kept at the predetermined concentration levels (within the predetermined concentration ranges). That is, the amount of the copper ions consumed on the lower surface of the wafer W or the dummy wafer W should substantially be equalized with the amount of the copper ions leaching out of the copper tubes 146, and the amount of the divalent iron ions occurring in the vicinity of the anode 76 should substantially be equalized with the amount of the trivalent iron ions occurring in the vicinity of the copper tubes 146.

[0298] The copper ion consumption rate at which the copper ions are consumed in the plating liquid by the plating is determined by the operation statuses of the respective plating units 20 a to 20 d. The copper ion leaching rate at which the copper ions leach into the plating liquid from the copper tubes 146 in the copper dissolution tank 110 a is determined by the surface area of the copper tubes 146 in contact with the plating liquid, the flow rate of the plating liquid flowing in the vicinity of the copper tubes 146 and the concentration of the trivalent iron ions in the plating liquid.

[0299] The inner and outer peripheral surface areas of the copper tube 146 account for a major percentage of the total surface area of the copper tube 146. As the dissolution of the copper tube 146 proceeds, the thickness and length of the copper tube 146 are reduced. However, the reduction rate of the length is negligible. Therefore, the outer and inner peripheral surface areas of the copper tube 146 (the total surface area of the copper tube 146) are considered to be virtually constant before complete dissolution of the copper tube 146, even if the dissolution of the copper tube 146 proceeds. Whether or not the copper tube 146 is very close to the complete dissolution is determined on the basis of the output signal of the weight meter 154 a, 154 b. The flow rate of the plating liquid flowing into the copper dissolution tank 110 a may be employed as the flow rate of the plating liquid flowing in the vicinity of the copper tubes 146.

[0300] Therefore, the system controller 155 determines the pumping rate of the pump P5 on the basis of the operation statuses of the plating units 20 a to 20 d and the output signal of the absorptiometer 66B indicative of the concentration of the iron ions. The pumping rate of the pump P5 is regulated at a predetermined level on the basis of the feedback of the output signal of the flow meter 123 to the system controller 155. Under such control, the amount of the copper ions supplied to the plating liquid is balanced with the amount of the copper ions consumed in the plating liquid to keep the copper ion concentration virtually constant in the plating liquid.

[0301] If the dissolution of the copper tubes 146 in the copper dissolution tank 110 a proceeds to an extremely high level, the total surface area of the copper tubes 146 is rapidly reduced, making it difficult to supply the copper ions to the plating liquid at a constant rate. To avoid such an event, the supply of the plating liquid to the copper dissolution tank 110 a is stopped when the weight of the copper tubes 146 in the copper dissolution tank 110 a is reduced below a predetermined level (e.g., 20% to 30% of the initial weight). Then, the supply of the plating liquid to the copper dissolution tank 110 b is started.

[0302] More specifically, when the system controller 155 judges on the basis of the signal of the weight meter 154 a that the weight of the copper tube 146 in the copper dissolution tank 110 a is reduced below the predetermined level, the valves AV4-1 and AV4-2 are opened and the valves AV3-1 and AV3-2 are closed under the control of the system controller 155. Thus, the plating liquid is circulated through the plating section 12 and the copper dissolution tank 110 b. Where the copper tubes 146 contained in the copper dissolution tank 110 b have a sufficient weight, the copper ions can stably be supplied into the plating liquid.

[0303] Since the two copper dissolution tanks 110 a, 110 b are provided in the major constituent managing section 2, the copper ions can constantly be supplied to the plating liquid without excess and deficiency. Thus, the surface of the wafer W can properly be copper-plated with the fine holes or grooves thereof properly filled with copper.

[0304] Next, an explanation will be given to the operation of the major constituent managing section 2 after the completion of the plating process in the plating section 12. If the plating liquid is circulated through the plating liquid container 55 and the copper dissolution tank 110 a or 110 b when the plating process is not performed in any of the plating units 20 a to 20 d, the concentration of the copper ions in the plating liquid is increased beyond the proper concentration range. This is because the copper ions are continuously supplied to the plating liquid from the copper tubes 146, though the copper ions are not consumed.

[0305] If the circulation of the plating liquid is stopped, the surfaces of the copper tubes 146 in the copper dissolution tank 110 a, 110 b are irreversibly deteriorated. Therefore, the surface of the wafer W cannot properly be copper-plated with a poorer capability of filling the fine holes or grooves thereof with copper, when the plating process is performed again in any of the plating units 20 a to 20 d by resuming the circulation of the plating liquid.

[0306] To cope with this, the plating liquid in the copper dissolution tank 110 a, 110 b is replaced with the replacement liquid for prevention of the increase in the concentration of the copper ions in the plating liquid and the deterioration of the surfaces of the copper tubes 146 upon the completion of the plating process in the plating section 12. It is herein assumed that the plating liquid in the copper dissolution tank 110 a is replaced with the replacement liquid.

[0307] The deterioration of the surfaces of the copper tubes 146 may occur within several hours. On the other hand, the plating process is often resumed immediately after the completion of the plating process in the plating section 12 due to a change in the production plan. In this case, if the plating liquid in the copper dissolution tank 110 a is already replaced with the replacement liquid, the replacement liquid in the copper dissolution tank 110 a should be replaced again with the plating liquid. The time required for the replacement of the plating liquid in the copper dissolution tank 110 a is about 5 minutes to about 10 minutes, so that the productivity is reduced. Therefore, the plating liquid in the copper dissolution tank 110 a is replaced with the replacement liquid after a lapse of a 2- to 3-hour standby period from the completion of the plating process in the plating section 12.

[0308] If the plating process is less likely to be resumed immediately after the completion of the plating process in the plating section 12, the plating liquid in the copper dissolution tank 110 a may be replaced with the replacement liquid immediately after the completion of the plating process.

[0309] First, the pump P5 is stopped and all the valves in the major constituent managing section 2 are closed under the control of the system controller 155. In turn, the system controller 155 controls the pressure increasing/reducing section 164 to supply air into the buffer container 111. Thus, the internal pressure of the buffer container 111 is increased. Then, the valves AV2-2, AV3-1, AV3-2, AV1-5, AV1-2 are opened under the control of the system controller 155. Thus, air pressurized in the buffer container 111 is introduced into the annular space 145 through the branch circulation pipe 119 a, so that the plating liquid is forced out of the copper dissolution tank 110 a into the plating liquid container 55 in the plating section 12 through the branch circulation pipe 121 a.

[0310] The system controller 155 calculates the weight of the plating liquid in the copper dissolution tank 110 a on the basis of the output signal of the weight meter 154 a, and maintains the aforesaid conditions until it is judged that almost all the plating liquid is expelled from the copper dissolution tank 110 a. When the system controller 155 judges that almost all the plating liquid is expelled from the copper dissolution tank 110 a, the valve AV3-3 is opened for a predetermined period under the control of the system controller 155. Thus, the plating liquid remaining in the bottom portion of the copper dissolution tank 110 a is virtually completely discharged through the liquid outlet pipe 149 a.

[0311] Subsequently, the valve AV7-1 is opened under the control of the system controller 155 to introduce deionized water into the buffer container 111. When it is judged on the basis of the output signal of the constant volume heck sensor 126 that the surface of deionized water rises o reach the predetermined level in the buffer container 111, the valve AV7-1 is closed under the control of the system controller 155. Thus, a predetermined amount of deionized water is contained in the buffer container 111.

[0312] In turn, the valves in the major constituent managing section 2 except the three-way valves AV8-1, AV8-2, AV8-3 are closed, and air is exhausted from the buffer container 111 by the pressure increasing/reducing section 164 under the control of the system controller 155. Thus, the internal pressure of the buffer container 111 is reduced. Then, the valves AV6-1, AV6-3 are opened under the control of the system controller 155. Thus, the internal pressure of the measure cup 129 is also reduced, so that the undiluted replacement liquid is sucked into the measure cup 129 from the undiluted replacement liquid tank 128 through the undiluted replacement liquid transport pipe 130.

[0313] During this period, the system controller 155 monitors the output signal of the constant volume check sensor 133, and judges whether the surface of the undiluted replacement liquid in the measure cup 129 reaches the predetermined level. If it is judged that the surface of the undiluted replacement liquid reaches the predetermined level, the valves AV6-3, AV6-1 are closed under the control of the system controller 155. Thus, a predetermined volume of the undiluted replacement liquid is dispensed in the measure cup 129.

[0314] Then, the valves AV6-2, AV6-4 are opened under the control of the system controller 155. Thus, the internal pressure of the measure cup 129 is set at the atmospheric pressure, so that the undiluted replacement liquid is transported from the measure cup 129 into the buffer container 111 having a lower internal pressure through the undiluted replacement liquid transport pipe 131 and the undiluted replacement liquid supply pipe 124 and mixed with the deionized water in the buffer container 111. When it is judged by the system controller 155 on the basis of the output signal of the emptiness check sensor 134 that the measure cup 129 is empty, the valves AV6-2, AV6-4 are closed under the control of the system controller 155.

[0315] Thus, the replacement liquid which has a predetermined composition and a predetermined concentration (e.g., 10% sulfuric acid aqueous solution) is prepared in the buffer container 111.

[0316] In turn, the system controller 155 controls the valve AV8-3 to establish communication between the buffer container 111 and the atmosphere. Thus, the internal pressure of the buffer container 111 is set at the atmospheric pressure. Thereafter, the valves AV1-1, AV1-5, AV3-2, AV3-1, AV2-2 are opened, and the pump P5 is actuated under the control of the system controller 155. At this time, the pump P5 is operated only for a predetermined period, or operated until it is judged on the basis of the output signal of the weight meter 154 a that the copper dissolution tank 110 a is filled with the replacement liquid.

[0317] Thereafter, the pump P5 is stopped, and all the valves in the major constituent managing section 2 are closed under the control of the system controller 155. Then, the valves AV1-1, AV1-4 are opened under the control of the system controller 155, whereby the replacement liquid remaining in the buffer container 111 is drained. Thus, the replacement of the plating liquid in the copper dissolution tank 110 a with the replacement liquid is completed.

[0318] Thus, the increase in the copper ion concentration of the plating liquid can be prevented. Further, the deterioration of the surfaces of the copper tubes 146 can be prevented. Therefore, when the plating process is performed again in any of the plating units 20 a to 20 d by circulating the plating liquid through the plating section 12 and the copper dissolution tank 110 a (110 b) , the surface of the wafer W can properly be copper-plated with the fine holes and grooves thereof properly filled with copper. Even if a small amount of the replacement liquid of the sulfuric acid aqueous solution is mixed in the plating liquid, the replacement liquid does not adversely affect the plating liquid because sulfuric acid is a supporting electrolyte of the plating liquid.

[0319] In the replacement of the plating liquid with the replacement liquid, deionized water maybe introduced into and discharged from the copper dissolution tank 110 a before the introduction of the replacement liquid after the plating liquid is discharged from the copper dissolution tank 110 a. Thus, the copper dissolution tank 110 a is cleaned with deionized water, so that the amount of the plating liquid mixed in the replacement liquid can be reduced. The introduction of the deionized water into the copper dissolution tank 110 a can be achieved in substantially the same manner as the introduction of the replacement liquid into the copper dissolution tank 110 a, except that only deionized water is introduced into the buffer container 111 from the deionized water supply source (but the undiluted replacement liquid is not introduced after the introduction of the deionized water).

[0320] When the replacement liquid filled in the copper dissolution tank 110 a, 110 b is replaced again with the plating liquid, the following operation is performed. First, the replacement liquid is expelled from the copper dissolution tank 110 a, 110 b in substantially the same manner as when the plating liquid is expelled from the copper dissolution tank 110 a, 110 b for the replacement of the plating liquid with the replacement liquid. In this operation, however, the expelled replacement liquid is drained by closing the valve AV1-2 and opening the valve AV1-4 under the control of the system controller 155. Thereafter, all the valves in the major constituent managing section 2 are closed, and then the valves AV1-2, AV1-5, AV3-2, AV3-1, AV2-1, for example, are opened under the control of the system controller 155. Thus, the plating liquid is introduced into the copper dissolution tank 110 a.

[0321] Next, an explanation will be given to an operation to be performed by the plating section 12 after the completion of the plating process in the plating section 12.

[0322] Upon detection of the discontinuation of the loading of the wafer W in the plating unit 20 a to 20 d, the system controller 155 controls the transport controller 29 to take one of the dummy wafers D out of the cassette Cd and transport the dummy wafer D into one of the plating units 20 a to 20 d. The dummy wafers D are transported into the respective plating units 20 a to 20 d in the same manner.

[0323] In turn, the dummy wafers D are subjected to the plating process in the respective plating units 20 a to 20 d according to the program (recipe) stored in the storage device 155M under the control of the system controller 155. Where the electrically conductive film of the dummy wafer D is composed of gold or platinum, there is no possibility that impurities are leached into the plating liquid because only the electrically conductive film of the dummy wafer D is kept in contact with the plating liquid.

[0324] At this time, the amount of the electricity applied between the cathode 83 and the anode 76 by the plating power source 82 is reduced to the minimum level required to keep the copper tubes 146 in a proper surface state. That is, an energization period is limited (for example, by intermittent energization) , or the amperage of the electric current is reduced as compared with the plating process performed on the wafer W. This allows for power saving.

[0325] In this case, the pumping rate of the plating liquid supplied by the pump P5 (see FIG. 13) is automatically adjusted correspondingly to the amount of the copper ions consumed on the dummy wafer D under the control of the system controller 155. Thus, the copper ion concentration and the divalent and trivalent iron ion concentrations in the plating liquid are kept generally constant.

[0326] When the plating process is continued in the plating units 20 a to 20 d for a predetermined period or when a command for treating wafers W of another lot is applied to the system controller 155, the plating of the dummy wafer D is interrupted. In such a case, the system controller 155 controls the transport controller 29 to load the dummy wafer D into the bevel etching unit 21 a, 21 b for removal of the copper film formed on the dummy wafer D.

[0327] The bevel etching units 21 a, 21 b can merely deal with two dummy wafers D at a time, while the plating units 20 a to 20 d can perform the plating process on the four dummy wafers D at a time. Therefore, the copper film removing process is performed twice, for example, in the respective bevel etching units 21 a, 21 b for the removal of the copper films on the four dummy wafers D. Where the copper films each have a reduced thickness due to the application of a reduced amount of electricity in the plating process, the removal of the copper films in the bevel etching units 21 a, 21 b can be achieved in a short time. The electrically conductive gold or platinum films of the dummy wafers D can completely be exposed by the etching.

[0328] Thereafter, the upper and lower surfaces of the dummy wafers D are rinsed with the rinse liquid. As required, the dummy wafers D are loaded into the cleaning units 22 a, 22 b thereby to be further cleaned under the control of the system controller 155.

[0329] Where the command for the treatment of wafers W of another lot is issued, the system controller 155 thereafter controls the transport controller 29 to accommodate all the dummy wafers D in the cassette Cd and then start the treatment of the wafers W.

[0330] On the other hand, where the command for the treatment of wafers W of another lot is not issued, the system controller 155 controls the transport controller 29 to return the dummy wafers D into the plating units 20 a to 20 d to perform the plating process again on the dummy wafers D.

[0331] Thus, the plating process and the copper film removing process are repeatedly performed on the dummy wafers D, until the command for the treatment of wafers W of another lot is inputted to the system controller 155. When the command for the treatment of wafers W of another lot is issued during the plating process on the dummy wafers D, the dummy wafers D are subjected to the copper film removing process and the cleaning process and then accommodated in the cassette Cd.

[0332] Even during discontinuation of the plating process on the wafer W, copper ions are continuously leached out of the copper tubes 146 in the copper dissolution tank 110 a, 110 b by performing the plating process on the dummy wafers D. Thus, the deterioration of the surfaces of the copper tubes 146 can be prevented. Therefore, the surface of the wafer W can properly be copper-plated with the fine holes or grooves thereof properly filled with copper, whenever the plating process on the wafer W is resumed.

[0333] As described above, it is also possible to prevent the deterioration of the surfaces of the copper tubes 146 (copper supply source) by replacing the plating liquid with the replacement liquid in the copper dissolution tank 110 a, 110 b. In this case, there is no need for the electrical energization between the anode 76 and the cathode 83, so that the energy is saved and the deterioration of the plating liquid is prevented. In this case, however, time is required for replacing the plating liquid with the replacement liquid and replacing the replacement liquid with the plating liquid in the copper dissolution tank 110 a, 110 b as described above. Therefore, the treatment of the wafer W cannot immediately be started when the replacement liquid is contained in the copper dissolution tanks 110 a, 110 b. Further, about 200 ml to about 300 ml of the plating liquid, for example, is wasted for the replacement.

[0334] In contrast, where the plating process is performed on the dummy wafers D to keep the copper tubes 146 in a proper surface state, the plating process on the wafer W can be started immediately after the dummy wafers D are subjected to the copper film removing process, then cleaned and dried, and accommodated in the cassette Cd. The wafer W may be transported into the plating unit 20 a to 20 d so as to start the plating process on the wafer W during the copper film removing process on the dummy wafers D in the bevel etching units 21 a, 21 b. Further, the waste of the plating liquid can be eliminated which maybe entailed where the plating liquid is replaced with the replacement liquid.

[0335] On the other hand, the plating process on the dummy wafers D entails energy consumption for the electrical energization between the anode 76 and the cathode 83 and the deterioration of the plating liquid. Since the aforesaid two methods for keeping the copper tubes 146 in a proper surface state each have an advantage and a disadvantage, these methods may selectively be employed. Where the plating process on the wafer W is discontinued for two, three or more hours, for example, the plating liquid may be replaced with the replacement liquid in the copper dissolution tank 110 a, 110 b. Where the plating process on the wafer W is discontinued for a shorter period, the plating process on the dummy wafers D may be performed.

[0336] By keeping the dummy wafer D in contact with the surface of the plating liquid filled in the plating vessel 61 a to 61 d, the plating vessel 61 a to 61 d is lidded with the dummy wafer D. Therefore, the evaporation of the plating liquid can be prevented thereby to mitigate a change in the composition of the plating liquid, even when the apparatus is not electrically energized.

[0337] By continuously performing the plating process on the wafer W or the dummy wafer D in the plating unit 20 a to 20 d, the crystallization of the effective constituents of the plating liquid is prevented which may other wise occur due to the drying of the plating liquid adhering onto the sealing surface 80 s of the cathode ring 80. Where the plating process is discontinued for a long period, the effective constituents of the plating liquid are liable to be crystallized on the sealing surface 80 s. The crystals of the effective constituents prevent intimate contact between the wafer W and the abutment portion 80 a when the plating process on the wafer W is resumed. In addition, the crystals damage the sealing surface 80 s, resulting in a permanent sealing failure. Such events can be avoided by continuously performing the plating process for prevention of the drying of the sealing surface 80 s. Thus, the plaiting liquid is prevented from leaking from a gap between the abutment portion 80 a and the wafer W.

[0338] The plating process on the dummy wafer D is performed in the respective plating units 20 a to 20 d, so that the abutment portions 80 a in the plating units 20 a to 20 d are less liable to suffer from the sealing failure.

[0339] The plating process on the dummy wafer D is automatically started upon the discontinuation of the loading of the wafer W in the plating unit 20 a to 20 d, so that the operator does not have to perform any operation for discontinuation of the plating process on the wafer W. The dummy wafers D are each repeatedly used in the plating section 12 until the service life of the electrically conductive film thereof ends due to wear-out. Hence, there is no need to frequently perform a maintenance operation.

[0340] While one embodiment of the present invention has thus been described, the invention may be embodied in any other ways. The dummy wafers D are accommodated in the cassette C placed on the cassette stage 16 in the plating apparatus in accordance with the embodiment described above. However, a place for accommodating the dummy wafers D is not limited to the cassette C placed on the cassette stage 16, but may be any place which is accessible by the transport robot TR within the wafer treating section 1.

[0341] The units for removing the copper film formed on the dummy wafer D (for refreshing the dummy wafer D) are not limited to the bevel etching units 21 a, 21 b. For example, components required for the removal of the copper film may be attached to the plating units 20 a to 20 d or the cleaning units 22 a, 22 b. Alternatively, units (chambers) dedicated to the removal of the copper film may be provided in any position accessible by the transport robot TR. The method for the removal of the copper film formed on the dummy wafer D is not limited to the chemical etching, but may be an electrolytic etching, for example.

[0342] While the present invention has been described in detail by way of the embodiment thereof, it should be understood that the foregoing disclosure is merely illustrative of the technical principles of the present invention but not limitative of the same. The spirit and scope of the present invention are to be limited only by the appended claims.

[0343] This application corresponds to Japanese Patent Application No. 2002-318951 filed with the Japanese Patent Office on Oct. 31, 2002, the disclosure of which is incorporated herein by reference. 

What is claimed is:
 1. A plating apparatus comprising: a plating unit for performing a plating process with the use of a plating liquid for plating a to-be-treated substrate with copper; a dummy substrate container for accommodating a dummy substrate having a surface formed with an electrically conductive film; a dummy substrate transport mechanism for transporting the dummy substrate between the plating unit and the dummy substrate container; a substrate loading discontinuation detecting mechanism for detecting discontinuation of loading of the to-be-treated substrate in the plating unit; and a control section which performs a control operation so as to transport the dummy substrate from the dummy substrate container into the plating unit by means of the dummy substrate transport mechanism and perform the plating process on the surface of the dummy substrate formed with the electrically conductive film in the plating unit in response to the detection of the discontinuation of the loading of the to-be-treated substrate in the plating unit by the substrate loading discontinuation detecting mechanism.
 2. A plating apparatus as set forth in claim 1, further comprising: a film removing unit for performing a copper film removing process for removing a copper film formed on the dummy substrate subjected to the plating process in the plating unit, wherein the electrically conductive film is resistant to the copper film removing process performed in the film removing unit.
 3. A plating apparatus as set forth in claim 2, wherein the electrically conductive film is composed of gold or platinum.
 4. A plating apparatus as set forth in claim 1, further comprising a cassette stage for receiving thereon a cassette capable of accommodating the to-be-treated substrate to be subjected to the plating process in the plating unit, wherein the dummy substrate container is a cassette disposed on the cassette stage.
 5. A plating apparatus as set forth in claim 1, wherein the plating unit includes a plurality of plating units, wherein the dummy substrate includes a plurality of dummy substrates whose number is greater than the number of the plating units, wherein the dummy substrate container is capable of accommodating all the dummy substrates.
 6. A plating apparatus comprising: a plating unit for performing a plating process with the use of a plating liquid for plating a to-be-treated substrate with copper; and a film removing unit for performing a copper film removing process for removing a copper film formed on a dummy substrate subjected to the plating process in the plating unit.
 7. A plating method comprising: the step of detecting discontinuation of loading of a to-be-treated substrate in a plating unit which is adapted to perform a plating process for plating the to-be-treated substrate with copper; the step of transporting a dummy substrate having a surface formed with an electrically conductive film from a dummy substrate container into the plating unit; and a dummy plating step of performing a dummy plating process in the plating unit for plating the surface of the dummy substrate formed with the electrically conductive film after the detecting step.
 8. A plating method as set forth in claim 7, further comprising the step of transporting the dummy substrate into a film removing unit which is adapted to perform a copper film removing process, and removing a copper film formed on the dummy substrate by the dummy plating process in the film removing unit after the dummy plating step, wherein the electrically conductive film is resistant to the copper film removing process performed in the film removing unit.
 9. A plating method as set forth in claim 7, wherein the plating unit includes a plurality of plating units, wherein the dummy plating step comprises the step of performing the dummy plating process simultaneously in the respective plating units.
 10. A plating method comprising the steps of: transporting a dummy substrate into a plating unit which is adapted to perform a plating process for plating a to-be-treated substrate with copper, and performing a dummy plating process in the plating unit for plating the dummy substrate with copper, when the plating process is not performed on the to-be-treated substrate in the plating unit; and transporting the dummy substrate having a copper film formed by the dummy plating process into a film removing unit which is adapted to perform a copper film removing process, and removing the copper film formed on the dummy substrate in the film removing unit after the dummy plating step. 